What Berachah did he request?
Temurah 16a: A Berachah in Torah.
Malbim: Since he was born amidst evil [for his mother], he prayed for a Berachah to nullify the decree of the Ma'arachah, lest there be more evil.
How did he ask Hashem to increase his border?
Temurah 16a: With Talmidim. Malbim - i.e. with Chochmah.
'Rashi': It is with inheritances.
What is the meaning of "v'Haysah Yadecha Imi v'Asisa me'Ra'ah l'Vilti Atzvi"?
Temurah 16a: I will not forget my learning, I will have friends like myself, and the Yetzer ha'Ra should not divert me from learning. If You grant this, good. If not, "Atzvi," I will be sad until death.
'Rashi': If You will be with me to save me from evil, that no damage or pain will occur to me.
Radak: Yabetz was worried lest his name, based on Etzev (sadness), cause him sadness. He asked Hashem to make a sign for him, that no worldly evil will sadden him. Atzvi is Po'el Omed (the subject himself acts; I will not be sad). Or, it is Po'el Yotzei (acts on another) - no evil will sadden me.
Malbim: If Hashem will help me in Avodas Hashem, all worldly matters will be the same to me. I will rejoice over evil like over good - Gam Zu l'Tovah. Great Tzadikim merit Hashgachah, in which evil is reversed for them to good.
What did he accept to do if Hashem will fulfill his requests?
'Rashi': He made a vow, and fulfilled it. This is the source that when people pledge Tzedakah b'Tzibur, they give without a vow. Radak - the Sefer does not mention Yabetz' vow. Also "va'Yidar Yisrael? Im Nason Titen Es ha'Am ha'Zeh b'Yadi", the vow is not mentioned. Some say so about "va'Yidar Yakov? Im Yihyeh Elokim Imadi? 1 "
I.e. "v'Hayah Hashem Li lEi'lokim; veha'Even? Yihyeh Beis Elokim? A'asrenu Lach" was all part of the condition; the Torah did not record what Yakov accepted if Hashem will fulfill this. (PF)
What do we learn from "va'Yavei Elokim Asher Sha'al"?
Malbim: He had Hashgachah from Hashem. Also, he brought to Hashem what he requested - he widened the borders of Malchus Shamayim via spreading Torah, and all worldly matters were equal in his eyes.
