Here is an amazing vort for parshas Vayeshev and Miketz. (Please let me know if it makes you flip out.)
There are various connections between Dovid and the hand or hands. First off, Yehuda’s blessing is about his hand at the nape of the enemy, and Rashi says it refers to Dovid. Moreover, the gematria of Dovid is fourteen, which is the gematria of hand. Dovid also spells du yad,two hands. Similarly, Shlomo, Dovid’s son, was called yedidya, which contains yad yad, two hands. Moreover, Dovid is compared to Eisav (in looks and innate tendencies), and the pasuk states that the hands are the hands of Eisav.
The pasuk says about the beis hamikdash, koninu yadecha, that it was built with His two hands. Who built the beis hamikdash? Dovid and Shlomo, HaShem’s two hands!
Yehuda said to Yaakov about Binyamin, from my hand you will ask him, that he would protect Binyamin. From my hand also means from Dovid you will ask him (Binyamin).Just as Yehuda was responsible for Binyamin, Dovid was also responsible to make sure that Mordechai (from Binyamin’s tribe) would be born, by not killing Shimi Ben Gera. The gemarah says that this is why the Megila calls Mordechai, “ish Yehudi.”
We can now fathom why the Torah tells us that Zerach stook out his hand. The gemarah says that Peretz broke through in kingly fasion, so Dovid hamelech came from him. Memeilah, Zerach stook out his hand. He wanted Dovid to come from him! But his hand was pulled back and Zerach broke forth! So Dovid descended from him!