Matthew 24:13 “But he that shall endure unto the end, the same shall be saved.”
The simple answer to why a person has to endure till the end to be saved, is that it is not for the Christians.
Matthew 24:3,21 “And as he sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be? and what shall be the sign of thy coming, and of the end of the world? For then shall be great tribulation, such as was not since the beginning of the world to this time, no, nor ever shall be.”
The disciples were asking Jesus about what was going to happen at the time period at the end, which included the tribulation.
Matthew 24:15-16 “When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand:) Then let them which be in Judaea flee into the mountains.”
Jesus was referring to Jews (holy place, Judaea) in tribulation.
Christians do not go through the tribulation because we do not have to work for our salvation. Christians are separated.
1 Corinthians 1:7-8 “So that ye come behind in no gift; waiting for the coming of our Lord Jesus Christ: Who shall also confirm you unto the end, that ye may be blameless in the day of our Lord Jesus Christ.”
In the above passage, Christians are considered blameless until the end. Jesus Christ does the confirmation and endurance for Christians. By rightly dividing verses to different people and time periods, we resolve all these confusions.
In the above passage, it refers to saved Christians.
1 Corinthians 1:2 “Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, with all that in every place call upon the name of Jesus Christ our Lord, both their’s and our’s:”