What is the meaning of the saying of the Messenger of Allah, peace and blessings be upon him: "When one of you goes to his bed, let him dust it three times with the inside of his lower garment, for he does not know what might have come onto it after him"?

Al-Bukhari and Muslim narrated from Abu Hurairah that the Messenger of Allah (peace be upon him) said: "When one of you goes to his bed, let him brush off his bed with the inside of his lower garment, for he does not know what might have come upon it after him." "Goes to his bed" means returns to it for sleep, and "the inside of his lower garment" means the part that touches the body. The command to brush it off with that was explained as being to keep the outside clean, and because one does not know what insects or other things might have attached themselves to his bed.