"Then Jesus said to them again, 'Most assuredly, I say to you, I am the door of the sheep. All who ever came before Me are thieves and robbers, but the sheep did not hear them. I am the door. If anyone enters by Me, he will be saved, and will go in and out and find pasture. The thief does not come except to steal, and to kill, and to destroy. I have come that they may have life and that they may have it more abundantly" (John 10:7-10).
Here Jesus begins to explain His illustration from the beginning of the chapter and expand upon it.
The only way into the sheepfold is through the door, and Jesus is the door one must go through (cf. 10:9).
The "all" of John 10:8 is limited by the context and refers to those who came before Jesus who claimed to be the door of the sheep. They were really nothing more than "thieves and robbers" and the true "sheep did not hear them" (i.e., listen to and follow them). This statement would certainly be a reference to false Messiahs who appeared at various times in Israel's history. It would also include false teachers, such as the Pharisees, especially those who had attempted to turn the people away from the concept of the Messiah predicted by the prophets in order to promote the materialistic notion of a physical king and kingdom with splendor and military strength. Unfortunately, "thieves and robbers" still abound today spiritually. Anyone who teaches that the way of salvation is not through Jesus or not through the way Jesus set forth is a spiritual thief (as well as a liar).
Jesus plainly declared - "If anyone enters by Me, he will be saved." For a sheep to enter the fold through the door is for that sheep to enter into a place of safety. The implication here is that one cannot be saved without entering the fold through Christ (cf. 14:6). Acts 4:12 is abundantly clear on this point also - "Nor is there salvation in any other, for there is no other name [besides Jesus'] under heaven given among men by which we must be saved." Additionally, it is impossible to have proper access to God's sheep without going through Jesus (the door). In other words, fellowship to God's people begins with fellowship with God (cf. I John 1:7).
A sheep who enters through Jesus will "go in and out and find pasture" (John 10:9). This phrase is difficult to understand spiritually. It would seem to be a general reference to the abundant life mentioned in the following verse.
In 10:10, Jesus contrasts His intentions with that of a thief. A thief intends to steal, take life, and destroy. But Jesus came "that they may have life, and that they may have it more abundantly." Jesus is the source of all spiritual blessings (cf. Eph. 1:3). Jesus didn't come just to make the blessings of heaven available to mankind; He also came to provide a better way of life now. Being a disciple of His should result in a fuller, richer life in the present, a life that is spiritually focused and full of joy, hope, contentment, peace, and love. This is the abundant life, a life of bountiful, never-ending spiritual blessings that are only available "in Christ."