He had hope. "Well, if God will have me kill him that will not stop God's promise. He could raise him from the dead. Isaac will live." There was hope for life. And so, he went through it.
And that answered Isaac's question. They were in agreement. They walked together, because not only did Abraham have this hope, Isaac too had this hope because Abraham was an excellent father. The two went up on the mount in agreement that God would provide a lamb for the offering. And God did, in the next few verses.
