What is the Hadith of the Smile, at the end of which the Messenger of Allah, may Allah bless him and grant him peace, smiled?

The hadiths in which the Messenger of Allah, peace and blessings be upon him, smiled or laughed are numerous. Among them is what Al-Bukhari narrated from Abdullah ibn Umar, may Allah be pleased with both of them, that the Prophet, peace and blessings be upon him, besieged the people of Ta'if but did not conquer it. When he said, "Indeed, we are returning tomorrow, Allah willing," the Muslims objected. So he ordered them to fight the next day, and they sustained injuries. Then he said, "Indeed, we are returning tomorrow, Allah willing," and they rejoiced at that, whereupon the Messenger of Allah, peace and blessings be upon him, smiled.