What sort of doubts did Abraham have?

Abraham experienced doubts primarily regarding God's promises, particularly about having a son despite his and Sarah's old age. He questioned how he could become the father of a great nation when he was childless, leading him to consider alternative solutions like adopting his servant's child. Additionally, he expressed uncertainty about God's plan during the covenant-making process and when asked to sacrifice Isaac, showcasing his struggle between faith and fear. Ultimately, these doubts reflect the human experience of grappling with trust in divine promises.