Command to marry Zaynab bint Jahsh

وَإِذْ تَقُولُ لِلَّذِىٓ أَنْعَمَ ٱللَّهُ عَلَيْهِ وَأَنْعَمْتَ عَلَيْهِ أَمْسِكْ عَلَيْكَ زَوْجَكَ وَٱتَّقِ ٱللَّهَ وَتُخْفِى فِى نَفْسِكَ مَا ٱللَّهُ مُبْدِيهِ وَتَخْشَى ٱلنَّاسَ وَٱللَّهُ أَحَقُّ أَن تَخْشَىٰهُ ۖ فَلَمَّا قَضَىٰ زَيْدٌۭ مِّنْهَا وَطَرًۭا زَوَّجْنَٰكَهَا لِكَىْ لَا يَكُونَ عَلَى ٱلْمُؤْمِنِينَ حَرَجٌۭ فِىٓ أَزْوَٰجِ أَدْعِيَآئِهِمْ إِذَا قَضَوْا۟ مِنْهُنَّ وَطَرًۭا ۚ وَكَانَ أَمْرُ ٱللَّهِ مَفْعُولًۭا

Behold! Thou didst say to one who had received the grace of Allah and thy favour: "Retain thou (in wedlock) thy wife, and fear Allah." But thou didst hide in thy heart that which Allah was about to make manifest: thou didst fear the people, but it is more fitting that thou shouldst fear Allah. Then when Zaid had dissolved (his marriage) with her, with the necessary (formality), We joined her in marriage to thee: in order that (in future) there may be no difficulty to the Believers in (the matter of) marriage with the wives of their adopted sons, when the latter have dissolved with the necessary (formality) (their marriage) with them. And Allah's command must be fulfilled.

مَّا كَانَ عَلَى ٱلنَّبِىِّ مِنْ حَرَجٍۢ فِيمَا فَرَضَ ٱللَّهُ لَهُۥ ۖ سُنَّةَ ٱللَّهِ فِى ٱلَّذِينَ خَلَوْا۟ مِن قَبْلُ ۚ وَكَانَ أَمْرُ ٱللَّهِ قَدَرًۭا مَّقْدُورًا

There can be no difficulty to the Prophet in what Allah has indicated to him as a duty. It was the practice (approved) of Allah amongst those of old that have passed away. And the command of Allah is a decree determined.