It therefore becomes evident that the act of falling (khurūr) onto the chin is itself an intended form of worship, beloved to Allah. What is meant by khurūr is not pressing the chin to the ground the way the forehead is pressed; rather, falling onto the chin marks the beginning of bowing, while prostration is its culmination. The worshipper places his forehead—not his chin—on the earth, yet he first descends upon his chin. The chin is the final boundary of the face, its lowest point and the part closest to the ground; hence, when someone falls upon his chin, he is in fact lowering his face and head in humble submission to Allah, and from that moment he has already embarked upon prostration. Just as placing the forehead is the completion of the prostration, falling upon the chin is its opening, and a complete descent must originate from either standing or sitting.

Ibn ʿAbbās (may Allah be pleased with him) said about the verse, “And they fall upon their chins” (17:107), that it means: “upon their faces.”

Al-Zajjāj explained: “The one who falls while standing only falls upon his face. The chin, where the two jaws meet, is a cartilaginous part of the face; when he begins to fall, the nearest part of his face to the earth is the chin.”

Ibn al-Anbārī said: “The very first part of the person that reaches the ground is …”