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,

﴿يَـأَيُّهَا الَّذِينَ ءَامَنُواْ لاَ تَتَّخِذُواْ الْيَهُودَ وَالنَّصَـرَى أَوْلِيَآءَ﴾

(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,

﴿يَـأَيُّهَا الَّذِينَ ءَامَنُواْ لاَ تَتَّخِذُواْ الْيَهُودَ وَالنَّصَـرَى أَوْلِيَآءَ﴾

(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.

﴿يُسَـرِعُونَ فِيهِمْ﴾

(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,

﴿فَيُصْبِحُواْ﴾

(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,

﴿نَـدِمِينَ﴾

(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

﴿وَيَقُولُ الَّذِينَ ءَامَنُواْ أَهُـؤُلاءِ الَّذِينَ أَقْسَمُواْ بِاللَّهِ جَهْدَ أَيْمَـنِهِمْ إِنَّهُمْ لَمَعَكُمْ حَبِطَتْ أَعْمَـلُهُمْ فَأَصْبَحُواْ خَـسِرِينَ ﴾

(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.)

﴿يأَيُّهَا الَّذِينَ ءَامَنُواْ مَن يَرْتَدَّ مِنكُمْ عَن دِينِهِ فَسَوْفَ يَأْتِى اللَّهُ بِقَوْمٍ يُحِبُّهُمْ وَيُحِبُّونَهُ أَذِلَّةٍ عَلَى الْمُؤْمِنِينَ أَعِزَّةٍ عَلَى الْكَـفِرِينَ يُجَـهِدُونَ فِى سَبِيلِ اللَّهِ وَلاَ يَخَـفُونَ لَوْمَةَ لائِمٍ ذلِكَ فَضْلُ اللَّهِ يُؤْتِيهِ مَن يَشَآءُ وَاللَّهُ وَسِعٌ عَلِيمٌ - إِنَّمَا وَلِيُّكُمُ اللَّهُ وَرَسُولُهُ وَالَّذِينَ ءَامَنُواْ الَّذِينَ يُقِيمُونَ الصَّلوةَ وَيُؤْتُونَ الزَّكَوةَ وَهُمْ رَاكِعُونَ - وَمَن يَتَوَلَّ اللَّهَ وَرَسُولَهُ وَالَّذِينَ ءَامَنُواْ فَإِنَّ حِزْبَ اللَّهِ هُمُ الْغَـلِبُونَ ﴾

(54. O you who believe! Whoever from among you turns back from his religion (Islam), Allah will bring a people whom He will love and they will love Him; humble towards the believers, stern towards the disbelievers, fighting in the way of Allah, and never fearing the blame of the blamers. That is the grace of Allah which He bestows on whom He wills. And Allah is All-Sufficient for His creatures' needs, All-Knower.) (55. Verily, your Protector is Allah, His Messenger, and the believers, those who perform the Salah, and give Zakah, and they bow down.) (56. And whosoever takes Allah, His Messenger, and those who have believed, as protectors, then the party of Allah will be the victorious.)