Allah says:

[ادْعُوهُمْ لاًّبَآئِهِمْ هُوَ أَقْسَطُ عِندَ اللَّهِ]

(Call them (adopted sons) by their fathers, that is more just with Allah.) This is a command which abrogates the state of affairs that existed at the beginning of Islam, when it was permitted to call adopted sons after the man who adopted them. Then Allah commanded that they should be given back the names of their real fathers, and states that this was more fair and just. Al-Bukhari (may Allah have mercy on him) narrated that `Abdullah bin `Umar said: "Zayd bin Harithah, may Allah be pleased with him, the freed servant of the Messenger of Allah , was always called Zayd bin Muhammad, until (the words of the) Qur'an were revealed:

[ادْعُوهُمْ لاًّبَآئِهِمْ هُوَ أَقْسَطُ عِندَ اللَّهِ]

(Call them (adopted sons) by (the names of) their fathers, that is more just with Allah.)'' This was also narrated by Muslim, At-Tirmidhi and An-Nasa'i. They used to deal with them as sons in every respect, including being alone with them as Mahrams and so on. Hence Sahlah bint Suhayl, the wife of Abu Hudhayfah, may Allah be pleased with them both, said: "O Messenger of Allah! We used to call Salim our son, but Allah has revealed what He has revealed. He used to enter upon me, but I feel that Abu Hudhayfah does not like that. The Prophet said:

«أَرْضِعِيهِ تَحْرُمِي عَلَيْه»

(Breastfeed him and he will become your Mahram. )'' Hence when this ruling was abrogated, Allah made it permissible for a man to marry the ex-wife of his adopted son, and the Messenger of Allah married Zaynab bint Jahsh, the divorced wife of Zayd bin Harithah, may Allah be pleased with him, Allah said:

[لِكَىْ لاَ يَكُونَ عَلَى الْمُؤْمِنِينَ حَرَجٌ فِى أَزْوَاجِ أَدْعِيَآئِهِمْ إِذَا قَضَوْاْ مِنْهُنَّ وَطَراً]

(So that (in future) there may be no difficulty to the believers in respect of the wives of their adopted sons when the latter have no desire to keep them) (33:37). And Allah says in Ayat At-Tahrim:

[وَحَلَـئِلُ أَبْنَآئِكُمُ الَّذِينَ مِنْ أَصْلَـبِكُمْ]

(The wives of your sons from your own loins) (4:23). The wife of an adopted son is not included because he was not born from the man's loins. A "foster'' son through breastfeeding is the same as a son born from one's own loins, from the point of view of Shari`ah, because the Prophet said in the Two Sahihs:

«حَرَّمُوا مِنَ الرَّضَاعَةِ مَا يُحَرَّمُ مِنَ النَّسَب»

(Suckling makes unlawful as lineage does.) As for calling a person "son'' as an expression of honor and endearment, this is not what is forbidden in this Ayah, as is indicated by the report recorded by Imam Ahmad and the Sunan compilers -- apart from At-Tirmidhi -- from Ibn `Abbas, may Allah be pleased with him, who said: "We young boys of Banu `Abd Al-Muttalib came to the Messenger of Allah at the Jamarat; he slapped us on the thigh and said,

«(أُبَيْنِيَّ) لَا تَرْمُوا الْجَمْرَةَ حَتَّى تَطْلُعَ الشَّمْس»

(O my sons, do not stone the Jamarah until the sun has risen.) This was during the Farewell Pilgrimage in 10 AH.

[ادْعُوهُمْ لاًّبَآئِهِمْ]

(Call them by their fathers.) This is concerning Zayd bin Harithah, may Allah be pleased with him. He was killed in 8 AH at the battle of Mu'tah. In Sahih Muslim it is reported that Anas bin Malik, may Allah be pleased with him, said: "The Messenger of Allah said:

«يَابَنِي»

(O my son.)'' It was also reported by Abu Dawud and At-Tirmidhi.

[فَإِن لَّمْ تَعْلَمُواْ ءَابَاءَهُمْ فَإِخوَانُكُمْ فِى الدِّينِ وَمَوَلِيكُمْ]

(But if you know not their father's then they are your brothers in the religion and Mawalikum (your freed servants).) Here Allah commands that adopted sons should be given back their fathers' names, if they are known; if they are not known, then they should be called brothers in faith or freed servants, to compensate for not knowing what their real lineage is. When the Messenger of Allah left Makkah after performing his `Umrat Al-Qada', the daughter of Hamzah, may Allah be pleased with her, started following him, calling, "O uncle, O uncle!'' `Ali took her and said to Fatimah, may Allah be pleased with her, "Take care of your uncle's daughter,'' so she picked her up. `Ali, Zayd and Ja`far -- may Allah be pleased with them -- disputed over of which of them was going to take care of her, and each of them gave his reasons. `Ali said, "I have more right, because she is the daughter of my paternal uncle.'' Zayd said, "She is the daughter of my brother.'' Ja`far bin Abi Talib said: "She is the daughter of my paternal uncle and I am married to her maternal aunt -- meaning Asma' bint `Umays.'' The Prophet ruled that she should stay with her maternal aunt, and said:

«الْخَالَةُ بِمَنْزِلَةِ الْأُم»

(The maternal aunt has the same status as the mother.) He said to `Ali, may Allah be pleased with him,

«أَنْتَ مِنِّي وَأَنَا مِنْك»

(You belong to me and I belong to you.) He said to Ja`far, may Allah be pleased with him,

«أَشْبَهْتَ خَلْقِي وَخُلُقِي»

(You resemble me both in your looks and in your attitude.) And he said to Zayd, may Allah be pleased with him,

«أَنْتَ أَخُونَا وَمَوْلَانَا»

(You are our brother and our freed servant.) This Hadith contains a number of rulings, the most important of which is that the Prophet ruled according to the truth, and that he sought to appease all the disputing parties. His saying to Zayd, may Allah be pleased with him,

«أَنْتَ أَخُونَا وَمَوْلَانَا»

(You are our brother and our freed servant.) is as Allah says in this Ayah:

[فَإِخوَانُكُمْ فِى الدِّينِ وَمَوَلِيكُمْ]

(your brothers in faith and your freed servants. ) Then Allah says:

[وَلَيْسَ عَلَيْكُمْ جُنَاحٌ فِيمَآ أَخْطَأْتُمْ بِهِ]

(And there is no sin on you concerning that in which you made a mistake,) meaning, if you call one of them after someone who is not in fact his father, by mistake, after trying your best to find out his parentage, then Allah will not attach any sin to this mistake. This is like the Ayah in which Allah commands His servants to say:

[رَبَّنَا لاَ تُؤَاخِذْنَآ إِن نَّسِينَآ أَوْ أَخْطَأْنَا]

(Our Lord! Punish us not if we forget or fall into error) (2:286). It was reported in Sahih Muslim that the Messenger of Allah said:

«قَالَ اللهُ عَزَّ وَجَلَّ: قَدْ فَعَلْت»

(Allah says, "Certainly I did (so).'') In Sahih Al-Bukhari, it was recorded that `Amr bin Al-`As, may Allah be pleased with him, said: "The Messenger of Allah said:

«إِذَا اجْتَهَدَ الْحَاكِمُ فَأَصَابَ فَلَهُ أَجْرَانِ، وَإِنِ اجْتَهَدَ فَأَخْطَأَ فَلَهُ أَجْر»

(If the judge makes Ijtihad and reaches the right decision, he will have two rewards; if he makes Ijtihad and reaches the wrong decision, he will have one reward.) In another Hadith:

«إِنَّ اللهَ تَعَالى رَفَعَ عَنْ أُمَّتِي الْخَطَأَ وَالنِّسْيَانَ وَمَا يُكْرَهُونَ عَلَيْه»

(Allah will forgive my Ummah for mistakes, forgetfulness and what they are forced to do.) And Allah says here:

[وَلَيْسَ عَلَيْكُمْ جُنَاحٌ فِيمَآ أَخْطَأْتُمْ بِهِ وَلَـكِن مَّا تَعَمَّدَتْ قُلُوبُكُمْ وَكَانَ اللَّهُ غَفُوراً رَّحِيماً]

(And there is no sin on you concerning that in which you made a mistake, except in regard to what your hearts deliberately intend. And Allah is Ever Oft-Forgiving, Most Merciful.) meaning, the sin is on the person who deliberately does something wrong, as Allah says elsewhere:

[لاَّ يُؤَاخِذُكُمُ اللَّهُ بِالَّلغْوِ فِى أَيْمَـنِكُمْ]

(Allah will not call you to account for that which is unintentional in your oaths) (2:225). Imam Ahmad narrated from Ibn `Abbas that `Umar said: "Allah sent Muhammad with the Truth and revealed to him the Book. One of the things that was revealed in it was the Ayah of stoning, so the Messenger of Allah stoned [adulterers] and we stoned [them] after he died.'' Then he said, "We also used to recite, `Do not attribute yourselves to anyone other than your fathers, for this is disbelief, to attribute yourselves to anyone other than your fathers.''' The Messenger of Allah said:

«لَا تُطْرُونِي كَمَا أُطْرِيَ عِيسَى ابْنُ مَرْيَمَ عَلَيْهِ الصَّلَاةُ وَالسَّلَامُ، فَإِنَّمَا أَنَا عَبْدُاللهِ، فَقُولُوا: عَبْدُهُ وَرَسُولُه»

(Do not exaggerate in praising me as `Isa bin Maryam was praised upon him be peace and blessings. I am just a servant of Allah. Say, "He is His servant and Messenger.'') Or Ma`mar may have said:

«كَمَا أَطْرَتِ النَّصَارَى ابْنَ مَرْيَم»

(As the Christians praised the son of Maryam. ) This was also narrated in another Hadith:

«ثَلَاثٌ فِي النَّاسِ كُفْرٌ: الطَّعْنُ فِي النَّسَبِ، وَالنِّيَاحَةُ عَلَى الْمَيِّتِ، وَالْاسْتِسْقَاءُ بِالنُّجُوم»

(Three things that people do are parts of disbelief: slandering a person's lineage, wailing over the dead and seeking rain by the stars.)

[النَّبِىُّ أَوْلَى بِالْمُؤْمِنِينَ مِنْ أَنْفُسِهِمْ وَأَزْوَجُهُ أُمَّهَـتُهُمْ وَأُوْلُو الاٌّرْحَامِ بَعْضُهُمْ أَوْلَى بِبَعْضٍ فِى كِتَـبِ اللَّهِ مِنَ الْمُؤْمِنِينَ وَالْمُهَـجِرِينَ إِلاَّ أَن تَفْعَلُواْ إِلَى أَوْلِيَآئِكُمْ مَّعْرُوفاً كَانَ ذَلِكَ فِى الْكِتَـبِ مَسْطُوراً ]

(6. The Prophet is closer to the believers than themselves, and his wives are their mothers. And blood relations among each other have closer personal ties in the decree of Allah than the believers and the Muhajirin, except that you do kindness to those brothers. This has been written in the Book.)