Jesus uses the Parable of the Sheep in two sections of Scripture.
Some would say that the accounts of this specific parable are in conflict and seem to contradict each other especially among those who are antagonistic towards the Bible and, moreover, to the fact that the Bible is the inerrable, infallible word of God. They would say something like this, “… You see, the Bible is full of contradictions and here again, in two Gospels the same exact same parables are in direct conflict with each other and, therefore, the Bible contradicts itself… it cannot be the Word of God and neither is it applicable to our 21st-century society and culture…”
Well, in both cases, that is; both Parables about the Sheep, are the same analogy but used in two different contexts. Even a normal human being may very well use the same analogy and use it in various contexts depending on the application and the people one is speaking to. Matthew 18 uses the Parable of the Sheep in the context of those Christians that have gone astray and have backslidden, whereas, Luke 15 uses the same Parable in the context of those who are lost, admit they are lost, and then Jesus places this in contrast to the self-righteous and the self-sufficient and the elite-minded religious person who is forever pointing out the wrongs in someone else’s life and not being able to see their own sinful nature, even when [s]he is exposed to the light of the truth and yet still rejects that truth outrightly!
The Parable of the Lost Sheep
3So he told them this parable: 4“What man of you, having a hundred sheep, if he has lost one of them, does not leave the ninety-nine in the open country, and go after the one that is lost, until he finds it? 5And when he has found it, he lays it on his shoulders, rejoicing. 6And when he comes home, he calls together his friends and neighbours, saying to them, ‘Rejoice with me, for I have found my sheep that was lost.’ 7Just so, I tell you, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance.
10“See that you do not despise one of these little ones. For I tell you that in heaven their angels always see the face of my Father who is in heaven.d 12What do you think? If a man has a hundred sheep, and one of them has gone astray, does he not leave the ninety-nine on the mountains and go in search of the one that went astray? 13And if he finds it, truly, I say to you, he rejoices over it more than over the ninety-nine that never went astray. 14So it is not the will of my Father who is in heaven that one of these little ones should perish.
Shane Bryant (OMIN CLC, CLDIP, DDIV, ADIV)