Hadith: 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

عن عبد الرحمن بن عوف رضي الله عنه قال: خرج رسول الله صلى الله عليه وسلم ، فتوجه نحو صدقته فدخل، فاستقبل القبلة فَخَرَّ ساجداً، فأطال السجود حتى ظننت أن الله عز وجل قبض نفسه فيها، فَدَنَوْتُ منه، ثم جلستُ فرفع رأسه، فقال: من هذا؟ قلت عبد الرحمن، قال: ما شأنك؟ قلت: يا رسول الله سجدت سجدة خشيت أن يكون الله عز وجل قد قَبَضَ نَفْسَكَ فيها، فقال: إن جبريل -عليه السلام-، أتاني فَبَشَّرَنِي ، فقال: إن الله عز وجل يقول: من صلى عليك صَلَّيْتُ عليه، ومن سلم عليك سَلَّمْتُ عليه، فسجدت لله عز وجل شكراً.
[حسن] - [رواه أحمد]

‘Abdur-Rahmān ibn ‘Awf (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) set out heading to a place that he had given in charity. He entered it, faced the Qiblah, and fell to the ground in prostration. He remained prostrating for a long time, until I thought that Allah, the Almighty, had taken his soul in this prostration. So I got closer to him and sat. When he raised his head, he said: "Who is that?" I said: "‘Abdur-Rahmān." He said: "What do you want?" I said: "O Messenger of Allah, you prostrated for such a long time that I feared that Allah, the Exalted, had taken your soul." So he said: "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."
Hasan/Sound. - [Ahmad]

Explanation

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.