15:1-10 The parable of the lost sheep is very applicable to the great work of man's redemption. The lost sheep represents the sinner as departed from God, and exposed to certain ruin if not brought back to him, yet not desirous to return. Christ is earnest in bringing sinners home. In the parable of the lost piece of silver, that which is lost, is one piece, of small value compared with the rest. Yet the woman seeks diligently till she finds it. This represents the various means and methods God makes use of to bring lost souls home to himself, and the Saviour's joy on their return to him. How careful then should we be that our repentance is unto salvation!
4. leave the ninety and nine—bend all His attention and care, as it were, to the one object of recovering the lost sheep; not saying. "It is but one; let it go; enough remain."
go after … until, &c.—pointing to all the diversified means which God sets in operation for recovering sinners.