After Kayin murdered his brother Hevel, G-d decreed that “נָע וָנָד ת ִּֽהְיֶה בָאָרֶץ You shall be a wanderer and an exile in the land” (Gen. 4:12). Kayin did a partial teshuvah when he said to G-d (ibid, verse 13), “Is my iniquity too great to bear?” As a result, G-d lessened His decree and declared that no one would be allowed to kill him for seven generations (verse 15). In addition, the verse says (verse 16) that Kayin was punished in that ”וַיֵּשֶב בְאֶרֶץ נוֹד He dwelt in the land of Nod.” This indicates that, although originally G-d decreed that he would be both נָע וָנָד (wandering and exiled), in the end he was only punished to be נוֹד wandering. This means that he only had to wander within one land but did not have to be constantly exiled from one land to another (Pesikta DeRav Kahan entry Shuvah, page 160).
Half-Baked Teshuvah Helps
Kayin’s teshuvah was not complete as he never expressed true remorse for his deed. All he did was ask G-d to bear his sin, i.e., that he should not be punished too badly. As such his punishment was lessened by half (see above), but he was not completely absolved. The lesson we can learn from this is that G-d accepts even a partial teshuvah and forgives to the extent of that level of teshuvah (Tzror HaMor by Rabbi Avaham Saba, on Gen. 4:16)
