The Believers do not befriend the Disbelievers
Allah the Exalted said,
[لاَّ تَجِدُ قَوْماً يُؤْمِنُونَ بِاللَّهِ وَالْيَوْمِ الاٌّخِرِ يُوَآدُّونَ مَنْ حَآدَّ اللَّهَ وَرَسُولَهُ وَلَوْ كَانُواْ ءَابَآءَهُمْ أَوْ أَبْنَآءَهُمْ أَوْ إِخْوَنَهُمْ أَوْ عَشِيرَتَهُمْ]
(You will not find any people who believe in Allah and the Last Day, making friendship with those who oppose Allah and His Messenger, even though they were their fathers or their sons or their brothers or their kindred.) Meaning, do not befriend the deniers, even if they are among the closest relatives. Allah said,
[لاَّ يَتَّخِذِ الْمُؤْمِنُونَ الْكَـفِرِينَ أَوْلِيَآءَ مِن دُونِ الْمُؤْمِنِينَ وَمَن يَفْعَلْ ذَلِكَ فَلَيْسَ مِنَ اللَّهِ فِي شَىْءٍ إِلاَ أَن تَتَّقُواْ مِنْهُمْ تُقَـةً وَيُحَذِّرْكُمُ اللَّهُ نَفْسَهُ]
(Let not the believers take the disbelievers as friends instead of the believers, and whoever does that will never be helped by Allah in any way, except if you indeed fear a danger from them. And Allah warns you against Himself.) (3:28), and,
[قُلْ إِن كَانَ ءَابَاؤُكُمْ وَأَبْنَآؤُكُمْ وَإِخْوَنُكُمْ وَأَزْوَجُكُمْ وَعَشِيرَتُكُمْ وَأَمْوَلٌ اقْتَرَفْتُمُوهَا وَتِجَـرَةٌ تَخْشَوْنَ كَسَادَهَا وَمَسَـكِنُ تَرْضَوْنَهَآ أَحَبَّ إِلَيْكُمْ مِّنَ اللَّهِ وَرَسُولِهِ وَجِهَادٍ فِي سَبِيلِهِ فَتَرَبَّصُواْ حَتَّى يَأْتِىَ اللَّهُ بِأَمْرِهِ وَاللَّهُ لاَ يَهْدِى الْقَوْمَ الْفَـسِقِينَ ]
(Say: If your fathers, your sons, your brothers, your wives, your kindred, the wealth that you have gained, the commerce in which you fear a decline, and the dwellings in which you delight are dearer to you than Allah and His Messenger, and striving hard and fighting in His cause, then wait until Allah brings about His decision (torment). And Allah guides not the people who are the rebellious.)(9:24) Sa`id bin `Abdul-`Aziz and others said that this Ayah,
[لاَّ تَجِدُ قَوْماً يُؤْمِنُونَ بِاللَّهِ وَالْيَوْمِ الاٌّخِرِ]
(You will not find any people who believe in Allah and the Last Day...) was revealed in the case of Abu `Ubaydah `Amir bin `Abdullah bin Al-Jarrah when he killed his disbelieving father, during the battle of Badr. This is why when `Umar bin Al-Khattab placed the matter of Khilafah in the consultation of six men after him, he said; "If Abu `Ubaydah were alive, I would have appointed him the Khalifah.'' It was also said that the Ayah,
[وَلَوْ كَانُواْ ءَابَآءَهُمْ]
(even though they were their fathers), was revealed in the case of Abu `Ubaydah, when he killed his father during the battle of Badr, while the Ayah,
[أَوْ أَبْنَآءَهُمْ]
(or their sons) was revealed in the case of Abu Bakr As-Siddiq when he intended to kill his (disbelieving) son, `Abdur-Rahman, (during Badr), while the Ayah,
[أَوْ إِخْوَنَهُمْ]
(or their brothers) was revealed about the case of Mus`ab bin `Umayr, who killed his brother, `Ubayd bin `Umayr, during Badr, and that the Ayah,
[أَوْ عَشِيرَتَهُمْ]
(or their kindred) was revealed about the case of `Umar, who killed one of his relatives during Badr, and also that this Ayah was revealed in the case of Hamzah, `Ali and Ubaydah bin Al-Harith. They killed their close relatives `Utbah, Shaybah and Al-Walid bin `Utbah that day. Allah knows best. A similar matter is when Allah's Messenger consulted with his Companions about what should be done with the captives of Badr. Abu Bakr As-Siddiq thought that they should accept ransom for them so the Muslims could use the money to strengthen themselves. He mentioned the fact that the captured were the cousins and the kindred, and that they might embrace Islam later on, by Allah's help. `Umar said, "But I have a different opinion, O Allah's Messenger! Let me kill so-and-so, my relative, and let `Ali kill `Aqil (`Ali's brother), and so-and-so kill so-and-so. Let us make it known to Allah that we have no mercy in our hearts for the idolators.'' Allah said,
[أُوْلَـئِكَ كَتَبَ فِى قُلُوبِهِمُ الإِيمَـنَ وَأَيَّدَهُمْ بِرُوحٍ مِّنْهُ]
(For such He has written faith in their hearts, and strengthened them with Ruh from Himself.) means, those who have the quality of not befriending those who oppose Allah and His Messenger , even if they are their fathers or brothers, are those whom Allah has decreed faith, meaning, happiness, in their hearts and made faith dear to their hearts and happiness reside therein. As-Suddi said that the Ayah,
[كَتَبَ فِى قُلُوبِهِمُ الإِيمَـنَ]
(He has written faith in their hearts,) means, "He has placed faith in their hearts.'' Ibn `Abbas said that,
[وَأَيَّدَهُمْ بِرُوحٍ مِّنْهُ]
(and strengthened them with Ruh from Himself.) means, "He gave them strengths.'' Allah's statement,
[وَيُدْخِلُهُمْ جَنَّـتٍ تَجْرِى مِن تَحْتِهَا الاٌّنْهَـرُ خَـلِدِينَ فِيهَا رَضِىَ اللَّهُ عَنْهُمْ وَرَضُواْ عَنْهُ]
(And He will admit them to Gardens under which rivers flow, to dwell therein. Allah is well pleased with them, and they are well pleased with Him.) was explained several times before. Allah's statement,
[رِّضِىَ اللَّهُ عَنْهُمْ وَرَضُواْ عَنْهُ]
(Allah is well pleased with them, and they are well pleased with Him.) contains a beautiful secret. When the believers became enraged against their relatives and kindred in Allah's cause, He compensated them by being pleased with them and making them pleased with Him from what He has granted them of eternal delight, ultimate victory and encompassing favor. Allah's statement,
[أُوْلَـئِكَ حِزْبُ اللَّهِ أَلاَ إِنَّ حِزْبَ اللَّهِ هُمُ الْمُفْلِحُونَ]
(They are the party of Allah. Verily, the party of Allah will be the successful.) indicates that they are the party of Allah, meaning, His servants who are worthy of earning His honor. Allah's statement,
[أَلاَ إِنَّ حِزْبَ اللَّهِ هُمُ الْمُفْلِحُونَ]
(Verily, the party of Allah will be the successful.) asserts their success, happiness and triumph in this life and the Hereafter, in contrast to those, who are the party of the devil,
[أَلاَ إِنَّ حِزْبَ الشَّيْطَـنِ هُمُ الخَـسِرُونَ]
(Verily, the party of Shaytan will be the losers!) This is the end of the Tafsir of Surat Al-Mujadilah. All praise and thanks are due to Allah.
[3:115] meaning, their good deeds will not be lost with Allah. Rather, He will award them the best rewards,