Teshuvah

Repentance (Hebrew: תשובה‎‎, literally "return", pronounced "tshuva" or "teshuva") is one element of atoning for sin in Judaism.

A Jewish penitent is traditionally known as a baal teshuva (lit. "master of repentance" or "master of return") (Hebrew: בעל תשובה‎‎; for a woman: Hebrew: בעלת תשובה‎‎, baalat teshuva; plural: Hebrew: בעלי תשובה‎‎, baalei teshuva). An alternative modern term is hozer beteshuva (Hebrew: חוזר בתשובה‎‎) (lit. "returning in repentance").

According to the Talmud, God created repentance before He created the physical universe, making it among the first things created. (Nedarim 39b).

One should repent immediately. Because of Judaism's understanding of the annual process of Divine Judgment, Jews believe that God is particularly open to repentance during period from the beginning of the month of Ellul through the High Holiday season, i.e. Rosh HaShanah (the Day of Judgement), Aseret Yimei Teshuva (the Ten Days of Repentance), Yom Kippur (the Day of Atonement), and according to Kaballah, Hoshana Rabbah.

...
Wikipedia