민수기 5:4의 Parshanut

Bnei Yisroel did so. There was no difficulty from the point of view of those who had to command the metzora’im to go outside the Israelite camp, and that did not require warning. The difficulty might have been only from the perspective of the metzora’im, who had to be asked to leave the Cloud of Glory, and perhaps an argument would arise. However, the metzora’im accepted this command with joy, to attain atonement for their sin. Thus, it was not as if they harkened to a warning, but rather as if they easily fulfilled the word of Hashem as well.