What earlier example of giving a tenth did Les connect to Abraham?
Abraham gave a tenth of the spoil after the kings had overrun Sodom. This earlier example of giving a tenth was connected to Abraham, showing that giving a tenth has been in Scripture since the very beginning of God's dealings with him, and Jacob later vows to give a tenth.
Les explains that Jacob's vow to give a tenth connects back to Abraham. Les teaches that giving a tenth has been in Scripture since the very beginning of God's dealing with Abraham, specifically when Abraham gave the tenth of the spoil from the kings that had overrun Sodom. Les also notes that Jacob, at this point, is not yet a true believer and is bargaining with God, similar to battlefield statements where men promise to serve God if He brings them through alive.
And this stone, which I have set for a pillar, shall be God’s house: and of all that thou shalt give me I will surely give the tenth unto thee.
And blessed be the most high God, which hath delivered thine enemies into thy hand. And he gave him tithes of all.