Buraida said that he heard God’s Messenger say: “A human being has three hundred and sixty joints, upon each of them charity is due.” On being asked who was capable of doing that he replied, “It may be mucus in the mosque which you bury and something which you remove from the road; but if you do not find such, two rak’as in the forenoon (Dhuha) will suffice you.” Source: [ Hadith: Sahih Al-Albani ]
As most joints are too small to be observed with the naked eye, it was impossible for Prophet Mohammad (s) to have known their number in the human body. The exact number of joints was discovered with recent developments in the fields of anatomy and histology. However, the Prophet (s) accurately pinpointed their number fourteen centuries ago.
In addition, this hadith emphasizes the status and virtue of Dhuha prayer, two rakʿahs of which is sufficient as a charity on behalf of every joint in the body, and a sign of genuine gratitude to Allah.
The Prophet (s) said: “None is diligent in establishing Dhuha prayer except one who is oft-repentant (awwāb), and it is the prayer of the oft-repentant.” Source: [ Hadith: Sahih Al-Albani ]