God wants Abraham to sacrifice what?

Gen 22:2 says, “And he said, Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of.”  God wants Abraham to sacrifice Issac?  I thought through him he would build a great nation.  It must be a test cause god never goes back on a promise (if you believe that you havn’t been reading the bible with me this far.)  Abraham isn’t even protesting like he did for Lot.  Saved Lot and changed gods mind once but in the case of his beloved son, he must know it is a test.  Then again he did cast his other son into the wilderness to die.  He doesn't even seem upset.