Matthew 18:11-15

Mat 18:11 (KJB)
For the Son of man is come to save that which was lost.

This one small verse packs the entire reason that Jesus came to this earth. He came to save that which was lost. He first came to the lost sheep of Israel. (Mat 15:24 KJV) But he answered and said, I am not sent but unto the lost sheep of the house of Israel. Then He came to find the other lost sheep, the Gentiles. (John 10:16 KJV) And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd. This is the reason that Jesus puts out the warnings in the previous verses because the very ones who are lost in sin are the ones that Jesus came to save and those who put a stumbling block before those future Christians, they will pay the ultimate price with their eternal souls.

Mat 18:12 (KJB)
How think ye? if a man have an hundred sheep, and one of them be gone astray, doth he not leave the ninety and nine, and goeth into the mountains, and seeketh that which is gone astray?

Jesus then creates another object lesson for the disciples concerning the shepherd and their sheep. Jesus asks the question that if a man have a hundred sheep and one wanders off from the flock, would he not go into the mountains and seek to find the one which has gone astray? (Ezek 34:11 KJV) For thus saith the Lord GOD; Behold, I, even I, will both search my sheep, and seek them out. This is exactly the mission of the Lord Jesus Christ, that He came to earth to seek out His sheep according to Ezekiel 34:11. In those days several flocks might graze together and one might leave their flocks with another shepherd and go and find the one which was lost. So the disciples would have been familiar with this method. In the Scriptures, the mountains are used as a symbol of kingdoms. (Isa 2:2 KJV) And it shall come to pass in the last days, that the mountain of the Lord's house shall be established in the top of the mountains, and shall be exalted above the hills; and all nations shall flow unto it. This means that one can say there are the kingdom of the world or the kingdom of Satan. Jesus has come to seek after His lost sheep which would be grazing in the kingdom of Satan and bring them back to the flock to graze in His Kingdom, that is, to save them and give them eternal pasture. (John 10:9 KJV) I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.

Mat 18:13 (KJB)
And if so be that he find it, verily I say unto you, he rejoiceth more of that sheep, than of the ninety and nine which went not astray.

If the shepherd finds that one lost sheep, he will rejoice over the fact that he found the sheep. It will be more joyful than if he would rejoice over the ninety nine sheep that did not become lost. (Luke 15:10 KJV) Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth. The principle is that Heaven rejoices whenever a person becomes saved and is added to the flock and is no more lost. The other ninety nine sheep were there when the shepherd returned as they did not go anywhere but stayed put.

Mat 18:14 (KJB)
Even so it is not the will of your Father which is in heaven, that one of these little ones should perish.

(2 Pet 3:9 KJV) The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. The will of the Father is that every single person that He named to salvation before the foundation of the world, will become saved at some point in their life. Not one of the Elect of God is ever going to be lost because that is not Godís will. The free will crowd uses 2 Peter 3:9 to show that God does not desire any to perish. That is faulty understanding because it does not say that. It teaches that the will of God is that not one of the Elect will perish but all will become saved. Matthew 18:14 is a specific declaration that not one of those named to salvation will ever perish.  If God willed everyone to be saved, then everyone would be saved but as we can see that is not the case in this world.

Mat 18:15 (KJB)
Moreover if thy brother shall trespass against thee, go and tell him his fault between thee and him alone: if he shall hear thee, thou hast gained thy brother.

There is going to come a time or times in the life of a believer that someone is going to trespass against us and how we handle it also reveals our spiritual condition. When someone commits a trespass against us, we are not to allow things to fester but we are to go to our brother privately and speak to them about their trespass. (Gal 6:1 KJV) Brethren, if a man be overtaken in a fault, ye which are spiritual, restore such an one in the spirit of meekness; considering thyself, lest thou also be tempted. We are to approach them with the mindset that their fault can become our fault if we do not watch it. We are to go to them and point out what they did wrong in meekness and not arrogantly. If they see the error of their way, then they will confess that they did wrongly and the relationship between the two brethren can be restored and the breach in the body of Christ will be fixed. If a disagreement is not fixed on this level, it can actually mushroom into a church split because sides will be drawn and otherwise innocent parties will be brought into the dispute and that will create a large rift in the body at that location and has the ability to spread beyond one location. That is why it is important to try and work out things on this level.