Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(And of them) i.e. of the hypocrites (is he who made a covenant with Allah) he who swore by Allah, the reference here is to Hatib Ibn Abi Balta'ah ((saying): If He give us of His bounty) the wealth that he has in Historic Syria (We will give alms) for the sake of Allah's religion: we shall give from it what is due to Allah and will use it to keep our ties of kinship (and become of the righteous) of the thankful.
And some of them have made a covenant with God [saying]: ‘If He gives us of His bounty, we will give voluntary alms (la-nassaddaqanna: the original tā’ [of natasaddaqanna] has been assimilated with the sād) and become of the righteous’: this was Tha‘laba b. Hātib, who asked the Prophet (s) to supplicate on his behalf so that God would give him wealth, of which he would give every needy person his due. He [the Prophet] thus supplicated for him and he became wealthy, but stopped attending the Friday prayer and congregational prayers and refused to pay the alms-tax, as God, exalted be He, says:
Allah says, some hypocrites give Allah their strongest oaths that if He enriches them from His bounty, they will give away alms and be among the righteous. However, they did not fulfill their vows or say the truth with their words. The consequence of this action is that hypocrisy was placed in their hearts until the Day they meet Allah the Exalted, on the Day of Resurrection. We seek refuge with Allah from such an end. Allah said,
بِمَآ أَخْلَفُواْ اللَّهَ مَا وَعَدُوهُ
(...because they broke that (covenant) with Allah which they had promised to Him) He placed hypocrisy in their hearts because they broke their promise and lied. In the Two Sahihs, it is recorded that the Messenger of Allah said,
(Know they not that Allah knows their secret ideas, and their Najwa,) Allah states that He knows the secret and what is more hidden than the secret. He has full knowledge of what is in their hearts, even when they pretend that they will give away alms, if they acquire wealth, and will be grateful to Allah for it. Truly, Allah knows them better than they know themselves, for He is the All-Knower of all unseen and apparent things, every secret, every session of counsel, and all that is seen and hidden.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
This is an instance of their ingratitude for which the hypocrites were rebuked in v. 74.
They broke their covenant with Allah which enjoined them to spend money in charity, if Allah enriched Them by His bounty. This shows that they were confirmed criminals and they did not care in the least for the agreements they made, and were niggardly and had no moral code to observe.
This refers to the mean conduct which the hypocrites evinced on the occasion of the appeal of the Holy Prophet for contributions towards the Tabuk expedition. The well-to-do hypocrites did not themselves make any contributions, but when the sincere Muslims came forward with generous contributions according to their means, they began to deride them. If a well-to-do Muslim made a handsome contribution, they would at once accuse him to be guilty of a 'showoff. On the other hand, if a poor Muslim contributed a paltry sum which he could hardly spare after sacrificing some of the barest necessities of his family or contributing the small earnings obtained by hard work, they would at once ridicule, saying, `Lo! Here is the farthing that will help conquer the forts of the Roman Empire!"
(And of them is he who made a covenant with Allah…) [9:75]. Abu'l-Hasan Muhammad ibn al-Fadl informed us> Abu 'Amr Muhammad ibn Ja'far ibn Matar> Abu 'Imran Musa ibn Sahl al-Jawni> Hisham ibn 'Ammar> Muhammad ibn Shu'ayb> Mu'adh ibn Rifa'ah al-Salami> Abu 'Abd al-Malik 'Ali ibn Yazid> al-Qasim ibn 'Abd al-Rahman> Abu Umamah al-Bahili said: “One day Tha'labah ibn Hatib al-Ansari went to the Messenger of Allah, Allah bless him and give him peace, and said: 'O Messenger of Allah, pray that Allah provides me with wealth'. The Messenger of Allah, Allah bless him and give him peace, said: 'Woe to you! A little for which you give thanks is better than plenty which you cannot bear'. Another time, he said to him: 'Do you not like to be like the Prophet of Allah. By Him in whose Hand is my soul, if I wanted mountains would flow with gold and silver for me'. Tha'labah said: 'By Him Who sent you with the truth, if you pray that Allah provides me with wealth, I will give each one his due'. The Messenger of Allah, Allah bless him and give him peace, then prayed: 'O Allah, give Tha'labah wealth!' Tha'labah then acquired some sheep and they multiplied like worms until Medina became too small to contain all his sheep. He left Medina and settled in one of its valleys. At that point, he only prayed Zuhr and 'Asr in congregation but not the other prescribed prayers. Then his sheep multiplied even more and he stopped praying in congregation altogether except for the Friday prayer. His sheep kept multiplying like worms until he finally stopped praying even the Friday prayer. The Messenger of Allah, Allah bless him and give him peace, asked about him and when they told him that his sheep had multiplied so much that he had to leave Medina and stopped praying in congregation, he said: 'Woe unto Tha'labah', he said it thrice. Then Allah, glorious and majestic is He, revealed (Take alms of their wealth, wherewith thou mayst purify them) [9:103] and He also revealed the obligation of Zakah. The Messenger of Allah, Allah bless him and give him peace, sent two men, one from Juhaynah and one from Banu Salim, to collect Zakat, and wrote for them instructions how to collect it. He also said to them: 'Go to Tha'labah and so-and-so from Banu Salim and collect their Zakah'. When they reached Tha'labah, read him the letter of the Messenger of Allah, Allah bless him and give him peace, and ask him for his Zakah, he said: 'This is nothing but the exemption tax (Jizyah)! This is nothing but the sister of the exemption tax! I do not know what this is; go finish your job and then come back to me'. The two men went to the man from Banu Salim and informed him about their business. The man selected the best of his camels and gave them for Zakah. When they saw this, they said: 'You are not obligated to do this, nor do we want to take this from you'. He said to them: 'No, you should take them, for I am happy to give them; they are my camels, after all'. They took those camels from him and when they finished their collection, they went back to Tha'labah. He said to them: 'Show me your letter', and after he read it he said: 'This is nothing but the sister of the exemption tax. Go back until I think about what I should do'. The two men left and went to see the Prophet, Allah bless him and give him peace, and the moment he saw them, he said: 'Woe to Tha'labah', before even saying a word to them. And he prayed that Allah bless the man from Banu Salim. The two men informed the Prophet about what Tha'labah and the man from Banu Salim did. Allah, glorious and majestic is He, revealed (And of them is he who made a covenant with Allah (saying): If He give us of His bounty we will give alms and become of the righteous) up to His words (… And because they lied) [9:79]. One of the relatives of Tha'labah was present with the Messenger of Allah, Allah bless him and give him peace, and he heard what the Prophet said about him. He went to Tha'labah and said to him: 'Woe unto you, O Tha'labah, Allah, exalted is He, has revealed about you this and that'. Tha'labah went to see the Prophet, Allah bless him and give him peace, and begged him to accept from him his Zakah. But the Prophet said to him: 'Allah has forbidden me from taking your Zakah'. Tha'labah then began dispersing dust on his head, upon which the Messenger of Allah, Allah bless him and give him peace, said to him: 'This is of your own doing! I commanded you and you did not obey me'. Tha'labah returned to his house. The Messenger of Allah, Allah bless him and give him peace, died and still did not accept anything from him. When Abu Bakr was sworn in as the new leader, Tha'labah went to see him and said: 'You know my status with the Messenger of Allah, Allah bless him and give him peace, as well as my position amongst the Helpers, so accept my Zakah'. Abu Bakr said: 'The Messenger of Allah, Allah bless him and give him peace, did not accept it and you expect me to accept it?' Abu Bakr died refusing to accept his Zakah. When 'Umar was selected as the leader of the Muslims, Tha'labah went to him and said: 'O leader of the believers, accept my Zakah!' 'Umar replied: 'The Messenger of Allah, Allah bless him and give him peace, did not accept it nor did Abu Bakr, so how do you expect me to accept it?' And he refused to take it from him until he died. When 'Uthman was chosen as Caliph, Tha'labah asked him to accept his Zakah, but 'Uthman said to him: 'The Messenger of Allah, Allah bless him and give him peace, did not accept nor did Abu Bakr and 'Umar, so how can I accept it from you'. And so 'Uthman did not accept his Zakah. Tha'labah died during 'Uthman's reign”.