'Ninety nine' in the Bible

What man of you, having a hundred sheep, if one of them gets loose and goes away, will not let the ninety-nine be in the waste land by themselves, and go after the wandering one, till he sees where it is?

I say to you that even so there will be more joy in heaven when one sinner is turned away from his wrongdoing, than for ninety-nine good men, who have no need of a change of heart.