Matthew 18:12 What 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? And if he finds it, truly, I say to you, he rejoices over it more than over the ninety-nine that never went astray. So it is not the will of my Father who is in heaven that one of these little ones should perish.
Psalms 119:176 I have gone astray like a lost sheep; seek your servant, for I do not forget your commandments.
Isaiah 53:6 All we like sheep have gone astray; we have turned—every one—to his own way; and the LORD has laid on him the iniquity of us all.
Ezekiel 34:16 I will seek the lost, and I will bring back the strayed, and I will bind up the injured, and I will strengthen the weak, and the fat and the strong I will destroy. I will feed them in justice.
Luke 15:4-7 “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? And when he has found it, he lays it on his shoulders, rejoicing. And when he comes home, he calls together his friends and his neighbors, saying to them, ‘Rejoice with me, for I have found my sheep that was lost.’ Just 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.
John 10:11 I am the good shepherd. The good shepherd lays down his life for the sheep.
John 10:14 I am the good shepherd. I know my own and my own know me,
1 Peter 2:25 For you were straying like sheep, but have now returned to the Shepherd and Overseer of your souls.
Ezekiel 34:12 As a shepherd seeks out his flock when he is among his sheep that have been scattered, so will I seek out my sheep, and I will rescue them from all places where they have been scattered on a day of clouds and thick darkness.
Isaiah 40:11 He will tend his flock like a shepherd; he will gather the lambs in his arms; he will carry them in his bosom, and gently lead those that are with young.
2 Peter 3:9 The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance.
For the Son of man is come to seek that which was lost. This is another, and stronger reason, why these little ones should not be despised; because Christ, who is here meant by the Son of man, came into this world to save these persons; who were lost in Adam, and had destroyed themselves by their transgressions, and carries great force in it: for if God had so great a regard to these little ones, as to send his Son to obtain eternal salvation for them, when they were in a miserable and perishing condition; and Christ had so much love for them, as to come into this world, and endure the sorrows, sufferings, and death itself for them, who were not only little, but lost; and that to obtain righteousness and life for them, and save them with an everlasting salvation; then they must, and ought to be, far above the contempt of all mortals; and the utmost care should be taken not to despise, grieve, offend, and injure them in any form or shape whatever.(Gill)
To show still further the reason why we should not despise Christians, he introduced a parable showing the joy felt when a thing lost is found. A shepherd rejoices over the recovery of one of his flock that had wandered more than over all that remained; so God rejoices that man is restored: so he seeks his salvation, and wills that not one thus found should perish. If God thus loves and preserves the redeemed, then surely man should not despise them. (Barnes)
The searching is not sure to be rewarded. Man’s sin and always leaning toward selfish, self-centered, self-worth, and self-reliance makes the result uncertain. No one may safely go on sinning, or living in neglectful, complacent, and careless unconcern, with the expectation of being finally found and saved. There must be a limit to the patience of God. If a man will not open his heart to the tugging of the Holy Spirit towards repentance and belief in the Gospel of Jesus Christ, he will not be found and brought home. God forces no one to be saved against his will.