Musar zu Jehoschua 7:19

Confession is a matter of great importance, for our Sages, of blessed memory, taught (Sanh. 43b) : When a man condemned to death was a distance of ten cubits from the place of stoning, they would say to him, "Confess." For it is the way of all who are about to be slain that they do confess, and every man who confesses has a share in the world to come. For thus have we found in the case of Achan. When Joshua said to him, "My son, give, I pray thee, glory to the Lord, the God of Israel, and confess unto him, and tell to me now what thou hast done, hide nothing from me." And Achan answered Joshua, and said, "It is true, I sinned to the Lord, the God of Israel and thus and like thus have I done" (Josh. 7:19—20). And how do we know that his confession atoned for him ? Because it is said, "And Joshua said, 'Why hast thou troubled us? The Lord shall trouble thee this day' " (Jos. 7:25). This day you will be troubled, but you will not be troubled in the world to come. And if he does not know how to confess, they say to him, "Say these words : 'May my death be an atonement for all my sins'."