When anything came to the Prophet ﷺ which caused pleasure (or, by which he was made glad), he prostrated himself in gratitude to Allah.  

عَنِ النَّبِيِّ ﷺ أَنَّهُ كَانَ إِذَا جَاءَهُ أَمْرُ سُرُورٍ أَوْ بُشِّرَ بِهِ خَرَّ سَاجِدًا شَاكِرًا لِلَّهِ  

We went out with the Messenger of Allah ﷺ from Mecca making for Medina. When we were near Azwara', he alighted, then raised his hands, and made supplication to Allah for a time, after which he prostrated himself, remaining a long time in prostration. Then he stood up and raised his hands for a time, after which he prostrated himself, remaining a long time in prostration. He then stood up and raised his hands for a time, after which he prostrated himself. Ahmad mentioned it three times. He then said: I begged my Lord and made intercession for my people, and He gave me a third of my people, so I prostrated myself in gratitude to my Lord. Then I raised my head and begged my Lord for my people, and He gave me a third of my people, so I prostrated myself in gratitude to my Lord. Then I raised my head and begged my Lord for my people and He gave me the remaining third, so I prostrated myself in gratitude to my Lord. Abu Dawud said: When Ahmad b. Salih narrated this tradition to us, he omitted the name of Ash'ath b. Ishaq, but Musa b. Sahl al-Ramli narrated it to us through him.  

خَرَجْنَا مَعَ رَسُولِ اللَّهِ ﷺ مِنْ مَكَّةَ نُرِيدُ الْمَدِينَةَ فَلَمَّا كُنَّا قَرِيبًا مِنْ عَزْوَرَا نَزَلَ ثُمَّ رَفَعَ يَدَيْهِ فَدَعَا اللَّهَ سَاعَةً ثُمَّ خَرَّ سَاجِدًا فَمَكَثَ طَوِيلاً ثُمَّ قَامَ فَرَفَعَ يَدَيْهِ فَدَعَا اللَّهَ سَاعَةً ثُمَّ خَرَّ سَاجِدًا فَمَكَثَ طَوِيلاً ثُمَّ قَامَ فَرَفَعَ يَدَيْهِ سَاعَةً ثُمَّ خَرَّ سَاجِدًا ذَكَرَهُ أَحْمَدُ ثَلاَثًا قَالَ إِنِّي سَأَلْتُ رَبِّي وَشَفَعْتُ لأُمَّتِي فَأَعْطَانِي ثُلُثَ أُمَّتِي فَخَرَرْتُ سَاجِدًا شُكْرًا لِرَبِّي ثُمَّ رَفَعْتُ رَأْسِي فَسَأَلْتُ رَبِّي لأُمَّتِي فَأَعْطَانِي ثُلُثَ أُمَّتِي فَخَرَرْتُ سَاجِدًا لِرَبِّي شُكْرًا ثُمَّ رَفَعْتُ رَأْسِي فَسَأَلْتُ رَبِّي لأُمَّتِي فَأَعْطَانِي الثُّلُثَ الآخَرَ فَخَرَرْتُ سَاجِدًا لِرَبِّي