Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(They hold that the clans) 'Abdullah Ibn Ubayy and his host think that the disbelievers of Mecca (have not retired (for good)) because of their fear and cowardice; it is also said: they think that the disbelievers of Mecca will not leave until they kill Muhammad (pbuh); (and if the clans) the disbelievers of Mecca (should advance (again), they) 'Abdullah Ibn Ubayy and his host (would fain be in the desert with the wandering Arabs) they would wish to leave Medina because of their fear and cowardice, (asking) in Medina (for the news of you) about your situation in the Ditch (and if they were among you) and if they were with you in the Ditch, (they would not give battle, save a little) out of ostentation and seeking fame.
They suppose that the confederates, of disbelievers, have not [yet] departed, to Mecca, because of their fear of them, and were the confederates to come, a second time, they would wish that they were in the desert with the Bedouins asking about your news, your encounters with the disbelievers. And if they were among you, this second time, they would fight but a little, for show and for fear of being reviled.
(and if the Confederates should come, they would wish they were in the deserts among the bedouins, seeking news about you;) means, `if the Confederates should come back, they hope that they will not be present with you in Al-Madinah, but that they will be in the desert, asking about news of you and what happened to you with your enemy.'
(and if they were to be among you, they would not fight but little.) means, `if they are among you, they will not fight alongside you very much,' because they are so cowardly and weak, and have so little faith, but Allah knows best about them.
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."