Allah tells what His Prophet said to his freed slave Zayd bin Harithah, may Allah be pleased with him, who was the one on whom Allah had bestowed grace, i.e., through Islam and following the Messenger .
وَأَنْعَمْتَ عَلَيْهِ
(and you have done a favor to him) means, by freeing him from slavery. And he was a great leader, held in high esteem and beloved by the Prophet . He was known as the beloved, and his son Usamah was known as the beloved son of the beloved. `A'ishah, may Allah be pleased with her, said: "The Messenger of Allah ﷺ never sent him on a campaign but he appointed him as its commander, and if he had lived after him he would have appointed him as his Khalifah." This was recorded by Imam Ahmad. The Messenger of Allah ﷺ had given him in marriage to the daughter of his paternal aunt, Zaynab bint Jahsh Al-Asadiyyah, may Allah be pleased with her, whose mother was Umaymah bint `Abd Al-Muttalib. For her dowery he gave her ten Dinars, sixty Dirhams, a veil, a cloak and a shirt, fifty Mudds of food and ten Mudds of dates. This was stated by Muqatil bin Hayyan. She stayed with him for a year, more or less, then problems arose between them. Zayd complained about her to the Messenger of Allah ﷺ, who told him, "Stay with your wife and have Taqwa of Allah." Allah says:
وَتُخْفِى فِى نِفْسِكَ مَا اللَّهُ مُبْدِيهِ وَتَخْشَى النَّاسَ وَاللَّهُ أَحَقُّ أَن تَخْشَـهُ
(But you did hide in yourself that which Allah will make manifest, you did fear the people whereas Allah had a better right that you should fear Him.) Ibn Jarir narrated that `A'ishah, may Allah be pleased with her, said, "If Muhammad ﷺ were to have concealed anything that was revealed to him of the Book of Allah, he would have concealed this Ayah:
وَتُخْفِى فِى نِفْسِكَ مَا اللَّهُ مُبْدِيهِ وَتَخْشَى النَّاسَ وَاللَّهُ أَحَقُّ أَن تَخْشَـهُ
(But you did hide in yourself that which Allah will make manifest, you did fear the people whereas Allah had a better right that you should fear Him.)"
فَلَمَّا قَضَى زَيْدٌ مِّنْهَا وَطَراً زَوَّجْنَـكَهَا
(So, when Zayd had completed his aim with her, We gave her to you in marriage,) meaning, `when her marriage to Zayd was over and he had separated from her, We married her to you,' and the One Who was her Wali (guardian) in this marriage was Allah Himself, in the sense that He revealed to the Prophet that he should go in unto her without any Wali, contractual agreement, dowery or witnesses among mankind. Imam Ahmad recorded that Thabit said that Anas, may Allah be pleased with him, said: "When Zaynab's `Iddah finished, may Allah be pleased with her, the Messenger of Allah ﷺ said to Zayd bin Harithah,
«اذْهَبْ فَاذْكُرْهَا عَلَي»
(Go to her and tell her about me (that I want to marry her).) So, he went to her and found her kneading dough. He (Zayd) said, `When I saw her I felt such respect for her that I could not even look at her and tell her what the Messenger of Allah ﷺ had said, so I turned my back to her and stepped aside, and said, `O Zaynab! Rejoice, for the Messenger of Allah ﷺ has sent me to propose marriage to you on his behalf.' She said, `I will not do anything until I pray to my Lord, may He be glorified.' So she went to the place where she usually prayed. Then Qur'an was revealed and the Messenger of Allah ﷺ came and entered without permission. We were there when she entered upon the Messenger of Allah ﷺ, and for the wedding feast we offered bread and meat. Then the people left, and some men stayed behind conversing in the house after they had eaten. The Messenger of Allah ﷺ went out and I followed him. He started to go around all the apartments of his wives, greeting them, and they said, `O Messenger of Allah ﷺ, how did you find your (new) wife' I do not know whether I or someone else told him that those people had left, so he went and entered the house, and I went to enter after him, but he drew the curtain between himself and I. The ruling of Hijab was revealed and he exhorted the people as Allah had exhorted them:
لاَ تَدْخُلُواْ بُيُوتَ النَّبِىِّ إِلاَّ أَن يُؤْذَنَ لَكُمْ
(Enter not the Prophet's houses, unless permission is given to you)." This was also recorded by Muslim and An-Nasa'i. Al-Bukhari, may Allah have mercy on him, recorded that Anas bin Malik, may Allah be pleased with him, said, "Zaynab bint Jahsh, may Allah be pleased with her, used to boast to the other wives of the Prophet , saying, `Your families arranged your marriages, but Allah arranged my marriage from above the seven heavens."' In (our Tafsir of) Surat An-Nur we mentioned that Muhammad bin `Abdullah bin Jahsh said: "Zaynab and `A'ishah, may Allah be pleased with them, were boasting to one another; Zaynab, may Allah be pleased with her, said, `I am the one whose marriage was revealed from above the heaven.' `A'ishah, may Allah be pleased with her, said, `I am the one whose innocence was revealed from heaven.' So, Zaynab conceded that, may Allah be pleased with her."
لِكَىْ لاَ يَكُونَ عَلَى الْمُؤْمِنِينَ حَرَجٌ فِى أَزْوَاجِ أَدْعِيَآئِهِمْ إِذَا قَضَوْاْ مِنْهُنَّ وَطَراً
(so that 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.) means, `We permitted you to marry her, and We did that so that there would no longer be any difficulty for the believers with regard to their marrying the ex-wives of their adopted sons.' Before prophethood, the Messenger of Allah ﷺ had adopted Zayd bin Harithah, may Allah be pleased with him, and he was known as Zayd, the son of Muhammad ﷺ. Allah put a stop to this when He said:
وَمَا جَعَلَ أَدْعِيَآءَكُمْ أَبْنَآءَكُمْ
(nor has He made your adopted sons your real sons) until:
ادْعُوهُمْ لاًّبَآئِهِمْ هُوَ أَقْسَطُ عِندَ اللَّهِ
(Call them after their fathers, that is more just with Allah) (33:4-5). Then this was confirmed and made even clearer by the marriage of the Messenger of Allah ﷺ to Zaynab bint Jahsh, may Allah be pleased with her, when Zayd bin Harithah divorced her. Allah says in Ayat At-Tahrim:
وَحَلَـئِلُ أَبْنَآئِكُمُ الَّذِينَ مِنْ أَصْلَـبِكُمْ
(the wives of your sons from your own loins) (4:23) which specifically excludes adopted sons. This custom (of adopting sons) was widespread among them.
وَكَانَ أَمْرُ اللَّهِ مَفْعُولاً
(And Allah's command must be fulfilled.) means, `this that has happened was decreed by Allah and was inevitable.' Allah knew that Zaynab, may Allah be pleased with her, would become one of the wives of the Prophet .