Hadith 31-12

وَبِهذَا الإِسنادِ قالَ: قالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَآلِهِ: أَتاني مَلَكٌ فَقالَ: يا مُحَمَّدُ إِنَّ اللَّهَ يُقرِئُكَ السَّلامَ وَيَقُولُ لَكَ: قَدْ زَوَّجتُ فاطِمَةَ مِن عَلِيِّ فَزَوِّجها مِنْهُ وَقَدْ أَمَرتُ شَجَرَةَ طُوبى‏ أَن تَحمِلَ الدُّرَّ وَالياقوتَ وَالمَرجانَ، وَإِنِّ أَهْل السَّماءِ قَدْ فَرَحوا بِذلِكَ وَسَيُولَدُ مِنْهُما وَلَدانِ سَيِّدا شَبابِ أَهْلِ الجَنَّةِ وَبِهِما يُزَيَّنُ أَهْلُ الجَنَّةِ فَأَبشِر يا مُحَمَّدُ فَإِنَّكَ خَيْرَ الأَوَّلِينَ وَالآخَرينَ.

According to the same documentation, God’s Prophet (S) said, “An angel came to me and said, O Muhammad! Indeed God sends you greetings and tells you, ‘I have married off (the Blessed Lady) Fatima to Ali. Therefore, give her to him in wedlock. I have ordered the ‘Tooba [9] tree to yield pearls, hyacinths and corals. Indeed all the residents of the Heavens are happy on this occasion. Soon they will have two sons who will be the Masters of the Youth in Paradise! The people of Paradise will be adorned by them. O Muhammad! Glad tidings! You are the best of the previous ones, and the best of the later ones.’”