Question:How could God bless all nations through Jacob after he deceitfully won Esau's blessing in Genesis 27. I thought lying was a sin.
Answer:The same way he could use Abraham, despite his lack of faith at first when he heard that he would have a child and despite his dishonesty about his wife Sarah before Pharaoh. The same way he could use Peter despite his having denied Jesus three times. The same way he could use Paul despite the fact that he had persecuted Christians, and was "the chief of sinners" (1 Timothy 1:16). The same way he could use David, despite his adultery with Bathsheba. The same way he could use Moses, despite the fact that he did not trust God at first and that he lost his temper and struck the rock. You get the idea. If God could not bless the nations through sinful people, then he could not bless the nations at all, because all of us are sinful. God has used me to a fairly significant extent in my teaching ministry. This is despite the fact that I am insensitive to my wife embarrassingly often and that I still struggle with pride and impure thoughts. I believe that God could bless the nations through you as well, and I doubt that you would claim before God to be less sinful than Jacob.
Yes, lying is a sin, but God, in his foreknowledge and in his predestination (See Romans 9:10-18.) was able to use the faith of sinful Jacob and sinful Isaac and sinful Abraham to bless all nations. All three of these patriarchs had great faith, despite the fact that they were sinners. This is the wisdom and the love of our God, that he could use the sin of Pharaoh to bless Israel and to bring salvation to his people. God even used Judas, indirectly, to bless all nations, as his betrayal led to the salvation of mankind. This can be confusing at first, but if we understand God's wisdom, his mercy and his love, then it tends to all fit into place. God predestined us all to salvation and he used sinful men and women to accomplish his purpose.