Jibrīl (peace be upon him) came to me and gave me glad tidings saying: “Allah, the Almighty, says: ’Whoever sends blessings on you, I will send blessings on him, and whoever sends greetings of peace to you, I will send greetings of peace to him.'" So I prostrated in thankfulness to Allah

This noble Hadīth clarifies the permissibility of the prostration of gratitude on receiving blessings, hearing good news, or receiving glad tiding, as happened to the Prophet (may Allah's peace and blessings be upon him). He was praying when Jibrīl (peace be upon him) came to him and brought him the glad tidings that whoever sends blessings on or greetings of peace to him from his Ummah, Allah will send His blessings on and greetings of peace to him.

Also, it is an act of Sunnah to prolong the prostration of gratitude, because the Prophet (may Allah's peace and blessings be upon him) did that until the Companions (may Allah be pleased with him) were worried that he might have died.