Why does Les say Abraham should not be blamed for having a child with Hagar?
Abraham had waited nearly fifty years after God's promise without seeing it fulfilled, so when God seemed inactive, he followed Sarah's suggestion and had a child by Hagar. The long delay and apparent silence made it understandable rather than blameworthy.
Les explains that Abraham's promises from God began back in Ur when he was probably about 50 years old. He did not leave Haran until he was 75, did not receive Ishmael until he was near 80, and only when he was 100 and Sarah was 90 did God perform and fulfill the promise. That meant Abraham had almost 50 years to “sweat the promises” while nothing happened. Les says that looking at those circumstances, he cannot blame Abraham for listening to Sarah and having a child by a slave girl, because it seemed God was not doing anything. Yet Les reminds us that God's wheels grind slowly but surely, and after 50 years of promises, the child finally came.