Sorry your thread got approved so late. Been busy :)
regarding the ayath 68:1, the tafsir you gave seems unauthentic. first of al nun is not a name of a fish but it's just a letter. Various surah's of the Qur'an begin with lettres, like alif lam min, ya sin, and so on the meaning of it is unknown to mankind.
Here is ibn kathir's tafsir about the specific verse:
In the Name of Allah, the Most Gracious, the Most Merciful.
[ن وَالْقَلَمِ وَمَا يَسْطُرُونَ - مَآ أَنتَ بِنِعْمَةِ رَبِّكَ بِمَجْنُونٍ - وَإِنَّ لَكَ لاّجْراً غَيْرَ مَمْنُونٍ - وَإِنَّكَ لَعَلَى خُلُقٍ عَظِيمٍ - فَسَتُبْصِرُ وَيُبْصِرُونَ - بِأَيِّكُمُ الْمَفْتُونُ - إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِمَن ضَلَّ عَن سَبِيلِهِ وَهُوَ أَعْلَمُ بِالْمُهْتَدِينَ ]
(1. Nun. By the pen and by what they Yastur.) (2. You, by the grace of your Lord, are not insane.) (3. And verily, for you will be reward that is not Mamnun.) (4. And verily, you are on an exalted character.) (5. You will see, and they will see,) (6. Which of you is afflicted with madness.) (7. Verily, your Lord is the best Knower of him who has gone astray from His path, and He is the best Knower of those who are guided.) We have already discussed the special letters of the Arabic alphabet at the beginning of Surat Al-Baqarah. Thus, Allah's saying,
(Nun), is like Allah's saying,
(Sad), and Allah's saying,
(Qaf), and similar to them from the individual letters that appear at the beginning of Qur'anic chapters. This has been discussed at length previously and there is no need to repeat it here.
I will copy paste those "previous discussions" here:
The Discussion of the Individual Letters
The individual letters in the beginning of some Surahs are among those things whose knowledge Allah has kept only for Himself. This was reported from Abu Bakr, `Umar, `Uthman, `Ali and Ibn Mas`ud. It was said that these letters are the names of some of the Surahs. It was also said that they are the beginnings that Allah chose to start the Surahs of the Qur'an with. Khasif stated that Mujahid said, "The beginnings of the Surahs, such as Qaf, Sad, Ta Sin Mim and Alif Lam Ra, are just some letters of the alphabet.'' Some linguists also stated that they are letters of the alphabet and that Allah simply did not cite the entire alphabet of twenty-eight letters. For instance, they said, one might say, "My son recites Alif, Ba, Ta, Tha... '' he means the entire alphabet although he stops before mentioning the rest of it. This opinion was mentioned by Ibn Jarir.
The Letters at the Beginning of Surahs
If one removes the repetitive letters, then the number of letters mentioned at the beginning of the Surahs is fourteen: Alif, Lam, Mim, Sad, Ra, Kaf, Ha, Ya, `Ayn, Ta, Sin, Ha, Qaf, Nun.
So glorious is He Who made everything subtly reflect His wisdom.
Moreover, the scholars said, "There is no doubt that Allah did not reveal these letters for jest and play.'' Some ignorant people said that some of the Qur'an does not mean anything, (meaning, such as these letters) thus committing a major mistake. On the contrary, these letters carry a specific meaning. Further, if we find an authentic narration leading to the Prophet that explains these letters, we will embrace the Prophet's statement. Otherwise, we will stop where we were made to stop and will proclaim,
[ءَامَنَّا بِهِ كُلٌّ مِّنْ عِندِ رَبِّنَا]
(We believe in it; all of it (clear and unclear verses) is from our Lord) (3:7).
The scholars did not agree on one opinion or explanation regarding this subject. Therefore, whoever thinks that one scholar's opinion is correct, he is obliged to follow it, otherwise it is better to refrain from making any judgment on this matter. Allah knows best.
These Letters testify to the Miraculous Qur'an
The wisdom behind mentioning these letters in the beginning of the Surahs, regardless of the exact meanings of these letters, is that they testify to the miracle of the Qur'an. Indeed, the servants are unable to produce something like the Qur'an, although it is comprised of the same letters with which they speak to each other. This opinion was mentioned by Ar-Razi in his Tafsir who related it to Al-Mubarrid and several other scholars. Al-Qurtubi also related this opinion to Al-Farra' and Qutrub. Az-Zamakhshari agreed with this opinion in his book, Al-Kashshaf. In addition, the Imam and scholar Abu Al-`Abbas Ibn Taymiyyah and our Shaykh Al-Hafiz Abu Al-Hajjaj Al-Mizzi agreed with this opinion. Al-Mizzi told me that it is also the opinion of Shaykh Al-Islam Ibn Taymiyyah. KAz-Zamakhshari said that these letters, "Were not all mentioned once in the beginning of the Qur'an. Rather, they were repeated so that the challenge (against the creation) is more daring. Similarly, several stories were mentioned repeatedly in the Qur'an, and also the challenge was repeated in various areas (i.e., to produce something like the Qur'an). Sometimes, one letter at a time was mentioned, such as Sad, Nun and Qaf. Sometimes two letters were mentioned, such as
(Ha Mim) (44:1) Sometimes, three letters were mentioned, such as,
(Alif Lam Mim (2: 1)) and four letters, such as,
(`Alif Lam Mim Ra) (13:1), and
(Alif Lam Mim Sad) (7:1).
Sometimes, five letters were mentioned, such as,
(Kaf Ha Ya `Ayn Sad) (19:1), and;
[حـم - تَنزِيلُ الْكِتَـبِ مِنَ اللَّهِ الْعَزِيزِ الْعَلِيمِ ]
(Ha Mim. `Ayn Sin Qaf) (42:1-2).
This is because the words that are used in speech are usually comprised of one, two, three, four, or five letters.''
Every Surah that begins with these letters demonstrates the Qur'an's miracle and magnificence, and this fact is known by those well-versed in such matters. The count of these Surahs is twenty-nine. For instance, Allah said,
[الم ذَلِكَ الْكِتَابُ لاَ رَيْبَ فِيهِ]
(Alif Lam Mim) This is the Book (the Qur'an), wherein there is no doubt (2:1-2),
[الم - ذَلِكَ الْكِتَابُ لاَ رَيْبَ فِيهِ هُدًى لِّلْمُتَّقِينَ نَزَّلَ عَلَيْكَ الْكِتَـبَ بِالْحَقِّ مُصَدِّقاً لِّمَا بَيْنَ يَدَيْهِ]
(Alif Lam Mim. Allah! La ilaha illa Huwa (none has the right to be worshipped but He), Al-Hayyul-Qayyuum (the Ever Living, the One Who sustains and protects all that exists). It is He Who has sent down the Book (the Qur'an) to you (Muhammad ) with truth, confirming what came before it.) (3:1-3), and,
[المص كِتَـبٌ أُنزِلَ إِلَيْكَ فَلاَ يَكُن فِى صَدْرِكَ حَرَجٌ مِّنْهُ]
(Alif Lam Mim Sad. (This is the) Book (the Qur'an) sent down unto you (O Muhammad ), so let not your breast be narrow therefrom) (7:1-2).
Also, Allah said,
[الر كِتَابٌ أَنزَلْنَـهُ إِلَيْكَ لِتُخْرِجَ النَّاسَ مِنَ الظُّلُمَـتِ إِلَى النُّورِ بِإِذْنِ رَبِّهِمْ]
(Alif Lam Ra. (This is) a Book which We have revealed unto you (O Muhammad ) in order that you might lead mankind out of darkness (of disbelief and polytheism) into the light (of belief in the Oneness of Allah and Islamic Monotheism) by their Lord's leave) (14:1),
[الم - ذَلِكَ الْكِتَابُ لاَ رَيْبَ فِيهِ هُدًى لِّلْمُتَّقِينَ ]
(Alif Lam Mim. The revelation of the Book (this Qur'an) in which there is no doubt, is from the Lord of the `Alamin (mankind, Jinn and all that exists)!) (32:1-2),
[حـم - تَنزِيلُ الْكِتَـبِ مِنَ اللَّهِ الْعَزِيزِ الْعَلِيمِ ]
(Ha Mim. A revelation from (Allah) the Most Gracious, the Most Merciful) (41:1-2), and,
[حـم - تَنزِيلُ الْكِتَـبِ مِنَ اللَّهِ الْعَزِيزِ الْعَلِيمِ - غَافِرِ الذَّنبِ وَقَابِلِ التَّوْبِ شَدِيدِ الْعِقَابِ ذِى الطَّوْلِ لاَ إِلَـهَ إِلاَّ هُوَ إِلَيْهِ الْمَصِيرُ ]
(Ha Mim. `Ain Sin Qaf. Likewise Allah, the Almighty, the Wise sends revelation to you (O Muhammad ) as (He sent revelation to) those before you.) (42:1-3).
There are several other Ayat that testify to what we have mentioned above, and Allah knows best.
Now that being said I will go back to the tafsir of 68:1
The Explanation of the Pen Concerning
(By the pen) The apparent meaning is that this refers to the actual pen that is used to write. This is like Allah's saying,
[اقْرَأْ وَرَبُّكَ الاٌّكْرَمُ - الَّذِى عَلَّمَ بِالْقَلَمِ - عَلَّمَ الإِنسَـنَ مَا لَمْ يَعْلَمْ ]
(Read! And your Lord is the Most Generous. Who has taught by the pen. He has taught man that which he knew not.) (96:3-5) Therefore, this statement is Allah's swearing and alerting His creatures to what He has favored them with by teaching them the skill of writing, through which knowledge is attained. Thus, Allah continues by saying,
(and by what they Yastur.) Ibn `Abbas, Mujahid and Qatadah all said that this means, "what they write.'' As-Suddi said, "The angels and the deeds of the servants they record.'' Others said, "Rather, what is meant here is the pen which Allah caused to write the decree when He wrote the decrees of all creation, and this took place fifty-thousand years before He created the heavens and the earth.'' For this, they present Hadiths that have been reported about the Pen. Ibn Abi Hatim recorded from Al-Walid bin `Ubadah bin As-Samit that he said, "My father called for me when he was dying and he said to me: `Verily, I heard the Messenger of Allah say,
«إِنَّ أَوَّلَ مَا خَلَقَ اللهُ الْقَلَمُ فَقَالَ لَهُ: اكْتُبْ، قَالَ: يَا رَبِّ وَمَا أَكْتُبُ؟ قَالَ: اكْتُبِ الْقَدَرَ وَمَا هُوَ كَائِنٌ إِلَى الْأَبَد»
(Verily, the first of what Allah created was the Pen, and He said to it: "Write.'' The Pen said: "O my Lord, what shall I write'' He said: "Write the decree and whatever will throughout eternity.'')'' This Hadith has been recorded by Imam Ahmad through various routes of transmission. At-Tirmidhi also recorded it from a Hadith of Abu Dawud At-Tayalisi and he (At-Tirmidhi) said about it, "Hasan Sahih, Gharib.''
Swearing by the Pen refers to the Greatness of the Prophet
[مَآ أَنتَ بِنِعْمَةِ رَبِّكَ بِمَجْنُونٍ ]
(You, by the grace of your Lord, are not insane.) meaning -- and all praise is due to Allah -- `you are not crazy as the ignorant among your people claim. They are those who deny the guidance and the clear truth that you have come with. Therefore, they attribute madness to you because of it.'
[وَإِنَّ لَكَ لاّجْراً غَيْرَ مَمْنُونٍ ]
(And verily, for you will be reward that is not Mamnun.) meaning, `for you is the great reward, and abundant blessings which will never be cut off or perish, because you conveyed the Message of your Lord to creation, and you were patient with their abuse.' The meaning of:
(not Mamnun) is that it will not be cut off. This is similar to Allah's statement,
[عَطَآءً غَيْرَ مَجْذُوذٍ]
(a gift without an end.) (11:108) and His statement,
[فَلَهُمْ أَجْرٌ غَيْرُ مَمْنُونٍ]
(Then they shall have a reward without end.) (95:6) Mujahid said,
(Without Mamnun) means "Without reckoning.'' And this refers back to what we have said before