When Adam sinned, he needed to descend into the physical world and elevate it by growing crops and eating them and using that energy to serve Hashem. Similarly, as a result of Yehuda’s sin of selling Yosef, he needed to descend to be involved in the story of marrying Tamar, who was his daughter-in-law. This story started when Yehuda married the daughter of Chira, and his sons (from this marriage) married Tamar, but died as a result of their sins. Afterwards, Tamar tricked Yehuda into marrying her. From this “unexpected” marriage came Peretz, who is the ancestor of Dovid Hamelech and Moshiach.
Similar to this process of descending into a seemingly unholy situation to redeem sparks of holiness that fell due to sins, we have a special prayer after Shemona Esrai called “Nefilas Apayim” or Tachanun. During this prayer we bend over and lower our heads and faces onto our arm as we ask Hashem for forgiveness for our sins. The reason for this lowering of the head is to symbolize that through our sins, we caused sparks of holiness to fall down into unholiness, and we need to go down and extract them from where they fell to.
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