Meaning of Iqamat As-Salah
Ibn `Abbas said that,
[وَيُقِيمُونَ الصَّلوةَ]
(And perform the Salah), means, "Perform the prayer with all of the obligations that accompany it.'' Ad-Dahhak said that Ibn `Abbas said, "Iqamat As-Salah means to complete the bowings, prostrations, recitation, humbleness and attendance for the prayer.'' Qatadah said, "Iqamat As-Salah means to preserve punctuality, and the ablution, bowings, and prostrations of the prayer.'' Muqatil bin Hayyan said Iqamat As-Salah means "To preserve punctuality for it, as well as completing ones purity for it, and completing the bowings, prostrations, recitation of the Qur'an, Tashahhud and blessings for the Prophet . This is Iqamat As-Salah.''

The Meaning of "Spending'' in this Ayah
`Ali bin Abi Talhah reported that Ibn `Abbas said,
[وَمِمَّا رَزَقْنَـهُمْ يُنفِقُونَ]
(And spend out of what We have provided for them) means, "The Zakah due on their wealth.'' As-Suddi said that Abu Malik and Abu Salih narrated from Ibn `Abbas, as well as Murrah from Ibn Mas`ud and other Companions of the Messenger of Allah , that,
[وَمِمَّا رَزَقْنَـهُمْ يُنفِقُونَ]
(And spend out of what We have provided for them) means, "A man's spending on his family. This was before the obligation of Zakah was revealed.'' Juwaybir narrated from Ad-Dahhak, "General spending (in charity) was a means of drawing nearer to Allah, according to one's discretion and capability. Until the obligation of charity was revealed in the seven Ayat of Surat Bara'ah (chapter 9), were revealed. These abrogated the previous case.''
In many instances, Allah mentioned prayer and spending wealth together. Prayer is a right of Allah as well as a form of worshipping Him. It includes singling Him out for one's devotion, praising Him, glorifying Him, supplicating to Him, invoking Him, and it displays one's dependence upon Him. Spending is form of kindness towards creatures by giving them what will benefit them, and those people most deserving of this charity are the relatives, the wife, the servants and then the rest of the people. So all types of required charity and required spending are included in Allah's saying,
[وَمِمَّا رَزَقْنَـهُمْ يُنفِقُونَ]
(And spend out of what we have provided for them). The Two Sahihs recorded that Ibn `Umar said that the Messenger of Allah said,
«بُنِيَ الْإِسْلَامُ عَلَى خَمْسٍ: شَهَادَةِ أَنْ لَا إِلهَ إِلَّا اللهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللهِ، وَإِقَامِ الصَّلَاةِ، وَإِيتَاءِ الزَّكَاةِ، وَصَوْمِ رَمَضَانَ، وَحَجِّ الْبَيْت»(Islam is built upon five (pillars): Testifying that there is no deity worthy of worship except Allah and that Muhammad is the Messenger of Allah, establishing the prayer, giving Zakah, fasting Ramadan and Hajj to the House.)
There are many other Hadiths on this subject.


The Meaning of Salah

In the Arabic language, the basic meaing of Salah is supplication. In religious terminology, Salah is used to refer to the acts of bowing and prostration, the remaining specified acts associated with it, specificed at certain times, with those known conditions, and the characteristics, and requirements that are well-known about it.
[وَالَّذِينَ يُؤْمِنُونَ بِمَآ أُنزِلَ إِلَيْكَ وَمَآ أُنزِلَ مِن قَبْلِكَ وَبِالأْخِرَةِ هُمْ يُوقِنُونَ ]
(4. And who have faith in what is revealed to you and in what was revealed before you, and in the Hereafter they are certain.)
Ibn `Abbas said that,
[وَالَّذِينَ يُؤْمِنُونَ بِمَآ أُنزِلَ إِلَيْكَ وَمَآ أُنزِلَ مِن قَبْلِكَ]
(And who have faith in what is revealed to you and in what was revealed before you.) means, "They believe in what Allah sent you with, and in what the previous Messengers were sent with, they do not distinguish between (believing) them, nor do they reject what they brought from their Lord.''
[وَبِالأْخِرَةِ هُمْ يُوقِنُونَ]
(And in the Hereafter they are certain) that is the resurrection, the standing (on the Day of Resurrection), Paradise, the Fire, the reckoning and the the Scale that weighs the deeds (the Mizan). The Hereafter is so named because it comes after this earthly life.

Ibn Kathir