Luke 24:45-49 Then opened he their understanding, that they might understand the scriptures, (46) And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: (47) And that repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem. (48) And ye are witnesses of these things. (49) And, behold, I send the promise of my Father upon you: but tarry ye in the city of Jerusalem, until ye be endued with power from on high.
The whole purpose of Jesus' life and ministry was to pave the way for mankind to be afforded the opportunity to repent, and so that they might thereby have their sins remitted. It is the purpose of the church to save them that would believe (1 Corinthians 1:21) by preaching the Gospel to every creature (Mark 16:15). The Bible tells us that ALL have sinned and come short of the glory of God (Romans 3:23), but Jesus commanded in Luke 24 (above) that we should preach the message of Salvation to all nations. It is the infilling and indwelling of the holy Spirit of promise (Ephesians 1:13) that enables us to fulfill that God-given command.