Abram Refuses a Thread and Earns the Altar's Red Line

(Genesis 14:23:) "Not from a thread to a shoe-strap <will I take anything that is yours>." Why? Because the Holy One, blessed be He, has promised me that He will make me rich, as it is said (Genesis 12:2): "And I will make your name great." Should I then take from what is yours, so that you would say, "I have made Abram rich"? The Holy One, blessed be He, said: You said, "not from a thread." By your life, I Myself shall give to your children an altar with a thread of red dye encircling it, just as our Rabbis taught (in Mishnah Middot 3:1).