Behold, I am with you; I will guard you wherever you go, and I will return you to this soil; for I will not forsake you until I will have done what I have spoken to you. (28:15)
A chassid once came to R' Yisrael Friedman z"l (the Rizhiner Rebbe; died 1850) for advice. As he waiting his turn to see the rebbe, the rebbe's young son, Dovid Moshe (the future Chortkover Rebbe), approached him and asked him what he wanted.
"I need a yeshuah / salvation," the chassid said.
Young Dovid Moshe replied, "I'll wait here for you. I'd like to know what my father tells you."
A few minutes later, the man emerged and reported, "The rebbe assured me that Hashem will help."
"And what will be until He helps?" the boy asked.
"I really don't know," the man replied helplessly.
"Go back and ask my father," instructed little Dovid Moshe.
The man reentered and repeated the boy's question. Said, the rebbe, "Hashem will also help until He helps. There is proof of this in the Torah. Hashem promised Yaakov that He would not abandon him "until I will have done what I have spoken to you." Does this mean that Hashem will abandon Yaakov after He has fulfilled His promises? Obviously not! Rather, it means that Hashem will not refrain from caring for Yaakov even before He is ready to keep His promises to the patriarch.