Why does G-d repent?

 R’ Tzadok (Pri Tzadik Shabbos Teshuva 16): It mentions in Vayikra Rabbah (35:3) that a human king makes a decree for others but he himself does not observe it. In contrast G‑d observes all the mitzvos. Similarly it says in Berachos (6a) that G‑d wears tefilin and He prays. Therefore we need to understand what it means that G‑d keeps the mitzva of repentance? A possible answer is based on the Sukka (52b) that there are four things that G‑d has regret. One of them is that He created the yetzer harah. It is necessary to understand how it is relevant for G‑d to have regret and to change His desire. This can be answered according to the medrash we just cited that all the mitzvos and decrees that G‑d makes He Himself keeps them first.  This is related to Bereishis Rabbah 11:5) in which someone asked that if G‑d keeps Shabbos how is it possible for it to rain on Shabbos? Concerning this it says about the creation of man (Bereishis 1:26): Let us make man in our image. That means man will do that which bears similarity to G‑d’s deeds. This is like it says in Bava Basra (58a) that man compared to the Divine Presence is like a monkey before a person.  Thus it says about the observance of Shabbos (Shemos 20:8): Remember Shabbos to sanctify it because in 6 days He made the heavens and the earth and on the 7^th day He rested. Understanding it in this matter that man’s actions are not identical with G‑d’s but bear some similarity, we can explain the mitzva of repentance. The essence of it is having regret. In other words that a person should have regret concerning the past and what he has done. Concerning this understanding we say that G‑d in a manner of speaking had regret in order that man would also be able to have regret concerning his deeds. Thus we find in the Pesikta (#44) a parable about a king whose son became sick. The doctor gave the son some medicine but the son was afraid to take it. The king told his son that he would take the medicine first to show him that the medicine was good so that he would taste it afterwards. It mentions in Bereishis Rabba (27:4) this that it said in the generation of the Flood that G‑d had regret that He created the yetzer harah. This is to allude to our explanation, that by writing this about Himself it would be possible for thoughts of repentance and regret to be brought about for the generation of the Flood in order that He would not need to destroy the world.