Practice what you preach...
Dawah is an important part of our lives, it is our duty to convey our knowledge that we have about Islam through the Quran and Sunnah.
Allah says regarding inviting people to dawah.
ٱدْعُ إِلَىٰ سَبِيلِ رَبِّكَ بِٱلْحِكْمَةِ وَٱلْمَوْعِظَةِ ٱلْحَسَنَةِ ۖ وَجَـٰدِلْهُم بِٱلَّتِى هِىَ أَحْسَنُ ۚ إِنَّ رَبَّكَ هُوَ أَعْلَمُ بِمَن ضَلَّ عَن سَبِيلِهِۦ ۖ وَهُوَ أَعْلَمُ بِٱلْمُهْتَدِينَ
Invite ˹all˺ to the Way of your Lord with wisdom and kind advice, and only debate with them in the best manner. Surely your Lord ˹alone˺ knows best who has strayed from His Way and who is ˹rightly˺ guided. Surah Nahl 125
And He has praised those who give dawah
وَمَنْ أَحْسَنُ قَوْلًۭا مِّمَّن دَعَآ إِلَى ٱللَّهِ وَعَمِلَ صَـٰلِحًۭا وَقَالَ إِنَّنِى مِنَ ٱلْمُسْلِمِينَ
And whose words are better than someone who calls ˹others˺ to Allah, does good, and says, “I am truly one of those who submit."?
Surah Fussilat 33
Prophet peace be upon him said about dawah from ahadith.
Abu Hurairah (May Allah be pleased with him) reported:
Messenger of Allah (ﷺ) said, "If anyone calls others to follow right guidance, his reward will be equivalent to those who follow him (in righteousness) without their reward being diminished in any respect, and if anyone invites others to follow error, the sin, will be equivalent to that of the people who follow him (in sinfulness) without their sins being diminished in any respect".
[Muslim]. Riyad Salihin 174
When the Prophet (ﷺ) sent Mu`adh to Yemen, he said to him, "You are going to a nation from the people of the Scripture, so let the first thing to which you will invite them, be the Tauhid of Allah. If they learn that, tell them that Allah has enjoined on them, five prayers to be offered in one day and one night. And if they pray, tell them that Allah has enjoined on them Zakat of their properties and it is to be taken from the rich among them and given to the poor. And if they agree to that, then take from them Zakat but avoid the best property of the people."
Sahih Bukhari 7372
We are ordered to enjoin what is good and forbid what is evil. Therefore we should begin our dawah with family first because we have a better understanding of them and they deserve good ties of kinship, then people around us, and then other people from parts of the world. What we should preach first is Tawheed (Oneness of Allah), as it is the foundation of Islam.
But first, we should practice what we are preaching. Because we need to improve ourselves.
Allah says in Surah Baqarah 44
۞ أَتَأْمُرُونَ ٱلنَّاسَ بِٱلْبِرِّ وَتَنسَوْنَ أَنفُسَكُمْ وَأَنتُمْ تَتْلُونَ ٱلْكِتَـٰبَ ۚ أَفَلَا تَعْقِلُونَ
Do you preach righteousness and fail to practice it yourselves, although you read the Scripture? Do you not understand?
Imam Ibn Kathir wrote in his tafsir on this verse:
Qatadah commented on the verse:
"The Children of Israel used to command people to obey Allah, fear Him and perform Al-Birr. Yet, they contradicted these orders, so Allah reminded them of this fact."
The hadith says
Messenger of Allah (ﷺ) said, "A man will be brought on the Day of Resurrection and will be cast into Hell, and his intestines will pour forth and he will go round them as a donkey goes round a millstone. The inmates of Hell will gather round him and say: 'What has happened to you, O so-and-so? Were you not enjoining us to do good and forbidding us to do evil?' He will reply: 'I was enjoining you to do good, but was not doing it myself; and I was forbidding you to do evil, but was doing it myself".
[Al-Bukhari and Muslim].
Riyad Salihin 198
These are a warning to us. So we should be very careful when giving dawah. We should first implement the good deeds into our lives before preaching it, and get rid of the sins before forbidding people from doing it so.
For example, if one does not keep his beard while he is able to grow, and he encourages people to grow the beard, he has gone against Allah and His messenger. And if he stares at non-mahram women and talks with them unnecessarily, and he is forbidding his people from doing to do so, has gone against Allah and His messenger.
So we should enjoin ourselves first.
And Allah knows best.