Fortress of the Muslim
Hisn al-Muslim 242
Arabic hadith text
كَانَ النَّبيُّ صلى الله عليه وسلم إِذَا أَتَاهُ أَمْرٌ يَسُرُّهُ أَوْ يُسَرُّ بِهِ خَرَّ سَاجِداً شُكْراً لِلَّهِ تَبَارَكَ وَتَعَالَى
Translation
When something that pleased him happened to the Prophet, peace and blessings be upon him, or he received joyful news, he would fall prostrate in gratitude to Allah, Blessed and Exalted.