Contradiction with Genesis 21:12
It states that in Isaac shall Abraham's seed be called, which aligns with Hebrews 11:18 rather than contradicts it, showing God's explicit instruction about Isaac being the chosen lineage.
Genesis 21:12: And God said unto Abraham, Let it not be grievous in thy sight because of the lad, and because of thy bondwoman; in all that Sarah hath said unto thee, hearken unto her voice; for in Isaac shall thy seed be called.
Paradox #1
Hebrews 11:18 refers to God's promise regarding Abraham's descendants through Isaac. A possible theological conflict is that this seems to contradict God's earlier command to Abraham to sacrifice Isaac. This raises questions about God's nature and His promises, as it seems contradictory for God to promise descendants through Isaac while also commanding his sacrifice. This tension is often discussed in terms of faith and divine testing.
Paradox #2
Hebrews 11:18 may seem inconsistent because it mentions promises made to Abraham about his descendants through Isaac, yet earlier scriptures note that Abraham was instructed to offer Isaac as a sacrifice. This can appear contradictory as the promise of descendants through Isaac would be seemingly impossible if Isaac were sacrificed. This is seen as a test of faith that resolves with Isaac's survival, but the initial command could seem conflicting with the promise.