Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Then will the believers say) the sincere believers say to the hypocrites 'Abdullah Ibn Ubayy and his followers: (Are these) the hypocrites (they who swore by Allah their most binding oaths) when a man swears by Allah, he has sworn by his most binding oath (that they) the hypocrites (were surely with you) with the sincere ones: i.e. following your religion in secret? (Their works have failed) their works will be thwarted in this world, (and they have become the losers) by incurring punishment upon themselves.
And they say (read wa-yaqūlu, or just yaqūlu, to indicate a new [independent] sentence; or wa-yaqūla as a supplement to what follows), those who believe, to one another in amazement, when their secrets are revealed: ‘Are these the ones who swore by God their most earnest oaths, making the utmost effort thereby [to swear], that they were surely with you?, in religion. God, exalted be He, says: Their, good, works have failed, are invalid; and they have become, they have ended up as, the losers’, in this world, through ignominy, and in the Hereafter, through their punishment.
The Prohibition of Taking the Jews, Christians and Enemies of Islam as Friends
Allah forbids His believing servants from having Jews and Christians as friends, because they are the enemies of Islam and its people, may Allah curse them. Allah then states that they are friends of each other and He gives a warning threat to those who do this,
وَمَن يَتَوَلَّهُمْ مِّنكُمْ فَإِنَّهُ مِنْهُمْ
(And if any among you befriends them, then surely he is one of them.) Ibn Abi Hatim recorded that `Umar ordered Abu Musa Al-Ash`ari to send him on one sheet of balance the count of what he took in and what he spent. Abu Musa then had a Christian scribe, and he was able to comply with `Umar's demand. `Umar liked what he saw and exclaimed, "This scribe is proficient. Would you read in the Masjid a letter that came to us from Ash-Sham'' Abu Musa said, `He cannot.'' `Umar said, "Is he not pure'' Abu Musa said, "No, but he is Christian.'' Abu Musa said, "So `Umar admonished me and poked my thigh (with his finger), saying, `Drive him out (from Al-Madinah).' He then recited,
(O you who believe! Take not the Jews and the Christians as friends...)'' Then he reported that `Abdullah bin `Utbah said, "Let one of you beware that he might be a Jew or a Christian, while unaware.'' The narrator of this statement said, "We thought that he was referring to the Ayah,
(O you who believe! Take not the Jews and the Christians as friends, )'' Allah said,
فَتَرَى الَّذِينَ فِى قُلُوبِهِم مَّرَضٌ
(And you see those in whose hearts there is a disease...) A disease of doubt, hesitation and hypocrisy.
(they hurry to their friendship,) meaning, they rush to offer them their friendship and allegiances in secret and in public,
يَقُولُونَ نَخْشَى أَن تُصِيبَنَا دَآئِرَةٌ
(saying: "We fear lest some misfortune of a disaster may befall us.") They thus offer this excuse for their friendship and allegiances to the disbelievers, saying that they fear that the disbelievers might defeat the Muslims, so they want to be in favor with the Jews and Christians, to use this favor for their benefit in that eventuality! Allah replied,
فَعَسَى اللَّهُ أَن يَأْتِىَ بِالْفَتْحِ
(Perhaps Allah may bring a victory...) referring to the conquering of Makkah, according to As-Suddi.
أَوْ أَمْرٍ مِّنْ عِندِهِ
(or a decision according to His will) requiring the Jews and Christians to pay the Jizyah, as As-Suddi stated,
(Then they will become) meaning, the hypocrites who gave their friendship to the Jews and Christians, will become,
عَلَى مَآ أَسَرُّواْ فِى أَنفُسِهِمْ
(for what they have been keeping as a secret in themselves) of allegiances,
(regretful,) for their friendship with the Jews and Christians which did not benefit them or protect them from any harm. Rather, it was nothing but harm, as Allah exposed their true reality to His faithful servants in this life, although they tried to conceal it. When the signs that exposed their hypocrisy were compiled against them, their matter became clear to Allah's faithful servants. So the believers were amazed at these hypocrites who pretended to be believers, swearing to their faithfulness, yet their claims were all lies and deceit. This is why Allah said, s
(And those who believe will say, "Are these the men who swore their strongest oaths by Allah that they were with you'' All that they did has been in vain, and they have become the losers.)
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
This refers to the condition of the hypocrites during the period when the conflict between Islam and kufr had not yet come to any decisive conclusion. Although Islam had become a power by dint of the sacrifices of its followers, the opposing forces were also very powerful and there were equal chances of the victory of either side. The hypocrites, while living among the Muslims, wanted to keep good relations with the Jews and the Christians so that if the conflict ended in the defeat of the Muslims, they might safely take refuge with their enemies. Then there was also the economic factor; at that time the Jews and the Christians were economically the most powerful people in Arabia. The money-lending business was almost entirely in their hands and they had a strong economic hold upon the people. Moreover, the most fertile regions of Arabia were in their possession. This also led the hypocrites to preserve their old relations with them. In short, they considered it very dangerous to break relations with these people because of the conflict between Islam and kufr, for they feared that it might ruin them economically and politically.
That is, something short of a decisive victory that might convince the people that it was Islam that was ultimately going to win in the conflict.
All the good acts that they did as Muslims were lost because they lacked sincerity. The Prayers they offered, the Fast they observed, the Zakat dues they paid, and other things they did in obedience to the Islamic Law became null and void because there was no sincerity in them. They did not dedicate themselves wholly to Allah but had divided their loyalties equally between Allah and His rebels for the sake of their worldly interests.