Why is Repentance necessary?
Repentance is required by God, as the first step in Salvation. Before you are baptized, before you receive the Holy Ghost, you must repent.
The only ground on which a sinner can be accepted by God is repentance. There must be a change! Repentance is something that was preached to the Jews as well as the Gentiles in the following in the scriptures below:
When you come to the Lord repentant, and are ready to make that change, He will receive you with open arms for the bible declares that, ".... a broken and a contrite heart, O God, thou wilt not despise." (Psalms 51:17)