Jesus taught about the narrow gate in Matthew 7:13-14 and Luke 13:23-24. In both passages, entrance through the narrow gate is limited to only a small group of people. This has caused concern among some readers, who may wonder how narrow is the narrow gate?
Jesus tells us in John 10:9 that He is the gate (or door) through which all must enter eternal life. Jesus alone is "the way, the truth, and the life" (John 14:6). The deciding factor is whether a person will believe in Jesus, entering through Him as the gate.
By narrow, Jesus means exclusive. He claimed to be the only way to know God (John 14:6). Most people, even in Christianity, find it difficult to believe that God's indescribable gift of eternal life is absolutely free and that the only way to obtain it is to take Jesus at His word (John 11:25-26).
If the gate to eternal life is narrow and hard, and only a few find it, does that mean there will not be many people in heaven? Not at all. In John's vision of heaven , he saw a great multitude that no one could number, from all parts of the world in God's presence in eternity (Revelation 7:9-10). Though not all will enter through Jesus (so not all will be saved), many will, and will receive eternal life.
Like those who asked Jesus if only a few will be saved (Luke 13:23), many people today wonder about others’ salvation. But in His reply ("strive to enter through the narrow gate"), Jesus pointed back to the only person's salvation we can really know, asking, "Are you saved?" We must strive (literally "agonize") in order to enter and come in. Striving to enter through Jesus does not mean you can save yourself through good works. Salvation is not based on our works, but on faith in Jesus Christ (Ephesians 2:8-10).