الَّذِينَ لَا يُوْتُونَ الزَّكَاةَ
Those who give not the Zakah,
Ali bin Abi Talhah reported from Ibn Abbas that;
this means those who do not bear witness that there is no God except Allah.
This was also the view of Ikrimah.
This is like the Ayat;
قَدْ أَفْلَحَ مَن زَكَّـهَا
وَقَدْ خَابَ مَن دَسَّـهَا
Indeed he succeeds who purifies himself. And indeed he fails who corrupts himself. (91;9-10)
And;
قَدْ أَفْلَحَ مَن تَزَكَّى
وَذَكَرَ اسْمَ رَبِّهِ فَصَلَّى
Indeed whosoever purifies himself shall achieve success. And remembers (glorifies) the Name of his Lord, and prays. (87;14-15)
And;
فَقُلْ هَل لَّكَ إِلَى أَن تَزَكَّى
And say to him;"Would you purify yourself?" (79;18)
What is meant by Zakah here is purification of the soul, ridding oneself of all bad qualities, the worst of which is Shirk. The Zakah paid on one's wealth is so called because it purifies wealth, and it is a means of increasing it, blessing it and making it more beneficial, and a means of assisting one to use it in doing good deeds.
Qatadah said, "They withheld the Zakah of their wealth."
This is the apparent meaning according to many of the scholars of Tafsir, and this is the view favored by Ibn Jarir.
But the matter is subject to further examination, because the obligation of Zakah was instituted during the second year after the Hijrah to Al-Madinah, according to what is stated by several scholars. Yet this Ayah was revealed in Makkah. However, it is not unlikely that the principle of giving charity and Zakah was already in place and had been enjoined at the beginning of the Prophet's mission, as Allah says;
وَءَاتُواْ حَقَّهُ يَوْمَ حَصَادِهِ
but pay the due thereof on the day of their harvest, (6;141)
As for the details of Zakah and how it is to be calculated according to the Nusub, were explained in Al-Madinah. This is how we may reconcile between the two opinions. Similarly, prayer was originally enjoined before sunrise and before sunset at the beginning of the Prophet's mission; it was only on the Night of the Isra', a year and a half before the Hijrah, that Allah enjoined upon His Messenger the five daily prayers. The conditions and essential elements of prayer were explained later, in stages. And Allah knows best.
وَهُم بِالاْخِرَةِ هُمْ كَافِرُونَ
and they are disbelievers in the Hereafter.
Then Allah says;
إِنَّ الَّذِينَ امَنُوا وَعَمِلُوا الصَّالِحَاتِ لَهُمْ أَجْرٌ غَيْرُ مَمْنُونٍ