Genesis 22:8 ASV

How could Abraham say this? God hadn't explicitly promised this to him prior.
1. Was Abraham making something up because he didn't want to spook Isaac?
2. Was Abraham speaking out his hopes that somehow God would come through, but with no explicit promise to stand on?
3. Was Abraham inferring this because of God's promise to make a great nation out of him through Isaac - which would clearly require him being alive?
Certainly this passage doesn't offer us a universal promise of provision, but it does clearly show us God's capacity to provide when He chooses to.