From the Encyclopaedia Judaica 14:73
Repentance is a Prerequisite n: something that is necessary to end or to the carrying out of a function – prerequisite adj. for divine forgiveness: God will not pardon man unconditionally but waits for him to repent. In repentance man must experience genuine remorse for the wrong he has committed and then convert his acts. Two sub stages are discernible in the latter process: first, the negative one of ceasing to do evil (Isa. 33;15 ; Ps. 15; 24;4) and second the positive step of doing good (Isa. 1:17; 58:5 ff; Jer. 7:3; 26:13 ; Amos 5:14-15; Ps. 34:15-16; 37:27).
The Bible is rich in idioms describing man’s active role in the process of repentance e.g., “incline the heart to the Lord” ( Josh. 24:23), “Make oneself a new heart” (Ezek. 18:31), circumcise the heart”. (Jer. 4:4), “wash the heart” (Jer. 4:14), and “break one’s fallow ground” (Hos. 10:12).
However all these expressions of man’s penitential adj: of or relating to penitence or penance. activity are summarizes by one verb which dominates the Bible, (SHWB, ‘to return’) which develops ultimately into rabbinic concept of teshuvah, repentance. This root combines in itself both requisites of repentance: To turn from the evil and turn to the good. The motion of turning implies that sin is not an ineradicable stain but a straying from the path, and that by the effort of turning; a power God has given to all men, The sinner can redirect his destiny. That this concept of turning back (to YHVH יְהֹוָה
Hebrew Yəhōwā, one vocalization of the Tetragrammaton יהוה (YHWH), the proper name of the God of Israel in the Hebrew Bible/Old Testament. It is considered one of the seven names of God in Judaism and a form of God’s name in Christianity. Covenant making covenant keeping GOD. For more info click here) is not a prophetic innovation but goes back to Israel’s ancient traditions is clear from Amos, without bothering to explain it’s meaning (Amos 4:6-11). Neither he nor Isaiah stresses repentance, except in his earliest prophecy (1:16-18 to which the prophet adds 19 – 20 by way of interpretation and 27), not because in they believe it is insignificant, but because in their time the people had sinned to such an extent, that they had overstepped the limits of divine forbearance and the gates of repentance were closed (Amos 7; Isa. 6)
For Isaiah, the need to turn back indeed continues to play a role, but only for the few who will survive God’s Purge. This Surviving remnant will itself actively engage in a program of repentance to qualify for residence in the New Zion (e.g. Isa. 10:20-23; 17:7-8: 27:9; 29:18 ff.; 30:18-26; 31: 6-7; 32:1-8, 15ff.; 33:5-6). Indeed, the name of the prophet’s firstborn was imprinted with this message: “[Only] a remnant will return” (Shear-Jashub Isa. 7:3)
In the teaching of both Hosea and Jeremiah, on the other hand, the call to turn back is never abandoned. When Jeremiah despairs of man’s capability of self-renewal, he postulates that God will provide a “new heart” that will overcome sin and merit eternal forgiveness (31:32-33; 32:39-40; cf Deut 30:6; Ezek. 36:26-27).
*See also Forgiveness