Explanation of the hadith of Anas.

The Shaykh : Then he mentioned that Qays ibn Sa'd used to stand before the Prophet (peace and blessings be upon him) in the position of the chief of police before the prince. This means he would stand before him, ahead of him, like the chief of police who goes ahead of the prince so that no one who intends to kill him would be in his path. In this is an indication or evidence that this practice has been in use since ancient times: that the ruler, the imam, or his deputy has a guard before him to repel any aggression that might be directed at him.