Jesus’ promise that those who would endure until the end would be saved, must be interpreted in light of His second coming to bring salvation (Hebrews 9:28), and the imminent end of the Old Covenant world (John 2:15-17). The Church was eagerly anticipating the consummation of their atonement (their salvation) in the first century, and according to Jesus, those who would endure until the end of the Old Covenant age would receive it at his coming (parousia).
The Institute Of Fulfilled Eschatology