The King James Bible addresses repentance in several passages:
Acts 3:19 (KJV)
19 Repent ye therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord;
2 Chronicles 7:14 (KJV)
14 If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land.
1 John 1:9 (KJV)
9 If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
Luke 15:7 (KJV)
7 I say unto you, that likewise joy shall be in heaven over one sinner that repenteth, more than over ninety and nine just persons, which need no repentance.
Acts 2:38 (KJV)
38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.