when a servant (of Allah) prostrates himself, the seven limbs, i.e, his face, his palms, his knees and his feet prostrate along with him.
Sunan Abi Dawud Book 2, Hadith 501
← Previous Hadith I have been commanded, and sometimes the narrator said: Your prophet (ﷺ) was commanded to prostrate on seven limbs.

Sunan Abi Dawud Book 2, Hadith 500 Next Hadith → The Prophet (ﷺ) said: Both hands prostrate as the face prostrates. When one of you puts his face (on the ground) he should put his hands too (on the ground). And when he raises it, he should raise them too.

Sunan Abi Dawud Book 2, Hadith 502