Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Being sparing of their help to you (believers)) they claimed they took pity on the believers; it is also said that this means: they are too niggardly when it is a question of spending on the believers. (But when the fear) of the enemy (cometh, then thou (Muhammad) seet them) the hypocrites in the Ditch (regarding thee with rolling eyes like one who fainteth unto death) like the one suffering from the pangs of death. (Then, when the fear) of the enemy (departeth, they scald you with sharp tongues) they attack and vilify you (in their greed for wealth (from the spoil)) they are stingy when it comes to spending in the way of Allah. (Such) those who have such traits (have not believed) are not sincere in their faith. (Therefore Allah maketh their deeds fruitless) Allah thwarts their good deeds by means of their evil works. (And that) thwarting good deeds (is easy for Allah).
grudging to you, in their help (ashihha, ‘grudging’, is the plural of shahīh, and is a circumstantial qualifier referring to the subject [of the verb] ya’tūna, ‘they engage’). And when there is a panic, you see them looking at you, their eyes rolling like one, that is, like the look of one, or the rolling of one, fainting at death, in other words, [one] in the throes thereof; but when the panic subsides, and the spoils have been secured, they scald you, they hurt you, or they smite you, with [their] sharp tongues, in their greed for the riches, in other words, for the spoils, which they demand [greedily]. Those, they never believed, really. Therefore God has invalidated their works, and that, invalidation, is easy for God, by His will.
(Then when fear comes, you will see them looking to you, their eyes revolving like one over whom hovers death;) means, because of the intensity of their fear and terror; this is how afraid these cowards are of fighting.
(but when the fear departs, they will smite you with sharp tongues,) means, when security is restored, they will speak eloquently and nicely, claiming that they were the bravest and most chivalrous of men, but they are lying. Ibn `Abbas, may Allah be pleased with him, said:
(they will smite you) means, "they will start to talk about you.'' Qatadah said: "But when it comes to the booty, the most miserly of people and the worst to have to share the booty with are those who say, `Give us, give us, we were there with you,' but during battle they were the most cowardly and the most likely to fail to support the truth.'' They are miserly towards good, meaning that there is no goodness in them, for they have combined cowardice with lies and little good. Allah says:
(Such have not believed. Therefore Allah makes their deeds fruitless and that is ever easy for Allah.)
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, "Abandon this Prophet and do not become involved in dangers and afflictions only for the sake of the Faith and Truth. Live a life of ease and comfort as we do."
"Who are ever reluctant...: "Who are not at all willing to spend their energies, their time, their wealth, etc. in any way in which the true believers are expending whatever they have. Not to speak of exerting themselves and braving the dangers, they do not want to cooperate with the believers in anything with an open heart. "
Lexically, this verse has two meanings:
(1) "When you return victorious from a war, they receive you warmly, and try to impress you with a glib tongue that they too are sincere believers and they too have made their contribution to promote the cause of Islam, and therefore, they too deserve a share from the booty."
(2) "If victory is attained these people show great powers of the tongue at the time of the division of the spoils and make great demands for their shares, recounting their services to the cause of Islam."
That is, "Allah will make null and void all the prayers that they offered, all the fasts that they observed, the Zakat that they paid, and other good works that they did after embracing Islam, and will give them no reward for these. For Allah does not judge actions and deeds according to their external form but on the basis of the faith and sincerity underlying them. When the actions are altogether devoid of this quality, there will be mere show and, therefore, meaningless. Here, one thing is especially noteworthy. A clear verdict has been given about the people who professed to believe in Allah and His Messenger, offered the Prayers, observed the fast, gave the Zakat and co-operated with the Muslims in other good works, to the effect that they did not believe at all. This verdict has been given because when they were put to the test during the conflict between Islam and un-Islam, they showed double-facedness, preferred selfish interests above the interests of the Faith, and shirked offering their selves and their wealth and their energies for the protection of Islam. This shows that the real criterion of the judgment are not the apparent deeds but the loyalties of man. If a person is not loyal to God and His Way, his profession of the Faith and his worship and other good deeds are worthless."
That is, "As their deeds and actions do not carry any value, Allah renders them fruitless without the slightest hesitation; and as they do not have any power to resist Allah has no difficulty in destroying their deeds altogether."