Midrash sa 1 Mga Hari 21:29: Shir HaShirim Rabbah, Ein Yaakov (Glick Edition) & Pirkei DeRabbi Eliezer

“I am black,” this is referring to Ahab, as it is stated: “It was when Ahab heard these matters that he rent his garments [and placed sackcloth upon his flesh, and he fasted]” (I Kings 21:27). How much did he fast? Rabbi Yehoshua ben Levi said: Three hours. If he was accustomed to eat his meal at three hours, he ate at six, and if he would eat at six, he ate at nine. “He lay in sackcloth, and walked slowly” (I Kings 21:27). Rabbi Yehoshua ben Levi said: He walked barefoot.¹⁹¹One who walks barefoot often walks more slowly than usual. The point here is that although Ahab was a wicked king, and is therefore called “black,” he humbled himself before God and his repentance was accepted (see I Kings 21:29), and is therefore also “lovely.” [Similarly,] regarding Yehoram, what is written? “The people saw, and behold, the sackcloth was upon his flesh underneath” (II Kings 6:30).
Rabbi Levi Bar Ḥaita said three approaches in regard to this [verse]: I am black all the days of the week and I am lovely on Shabbat. I am black all the days of the year and I am lovely on Yom Kippur. I am black regarding the Ten Tribes and I am lovely regarding the tribes of Judah and Benjamin.
I am black in this world and I am lovely in the World to Come.

(Pr. 18, 5) It is not good to favor the wicked person. [This passage signifies that] it is not good for the wicked that indulgence is shown them (in this world by the Lord). It was not good for Achab that indulgence was shown him in this world by the Holy One, praised be He! as it is said (I Kings 21, 29) Hast thou seen how Achab has humbled himself before me? (Pr. 18, 5) to wrest [the cause of the] righteous in judgment. [This passage signifies that] it is well for the just that no indulgence is shown them by the Holy One, praised be He! in this world. Happy are Moses and Aaron, because no indulgence was shown them in this world by the Holy One, praised be He! as it is said (Num. 20, 12) Because ye have not confided in me, etc. But if you had confided in me, your time to depart from this world would not yet have arrived. Happy are the righteous; for, not only do they obtain divine grace for themselves, but they also transfer the same to their children and their children's children, until endless generations. More of Aaron's children were destined to be burnt like Nadab and Abihu, as it is said (Lev. 10, 12) That were left. But the divine grace of their parents preserved them. Woe unto the wicked; for not only do they attach guilt unto themselves, but they also cause guilt to be attached to their children and their children's children unto endless generations. Many sons belonged to Canaan who were worthy to be relied upon as was Tabi, the servant of Rabban Gamaliel; but the guilt of their father prevented them from becoming so.

THE POWER OF REPENTANCE
REPENTANCE and good deeds are a shield against punishment. Rabbi Ishmael said: If repentance had not been created, the world would not stand. But since repentance has been created, the right hand of the Holy One, blessed be He, is stretched forth to receive the penitent every day, and He says, Repent, ye children of men. "Repent, ye children of men" (Ps. 90:8). Know thou the power of repentance. Come and see from Ahab, king of Israel, for he had robbed, coveted, and murdered, as it is said, "Hast thou killed, and also taken possession?" (1 Kings 21:19). He sent and called for Jehoshaphat, king of Judah, who gave him thrice daily forty stripes, and in fasting and with prayer he rose up early and retired late, before the Holy One, blessed be He, and he did not return any more to his evil deeds. His repentance was accepted, as it is said, || "Seest thou how Ahab humbleth himself before me? Because he humbleth himself before me, I will not bring the evil in his days" (1 Kings 21:29).