Hisnul Muslim 242

Upon receiving pleasant news

كان النبي صلى الله عليه وسلم إذا أتاه أمر يسرهُ أو يسرُّ به خر ساجداً شكراً لله تبارك وتعالى

Whenever something happened that pleased him or made him happy, the Prophet would prostrate himself in gratitude to Allah, the Blessed, the All-Mighty.