What does Genesis 17:3 mean?

In the previous two verses, God appeared to Abram and told him to walk before the Lord and to be blameless. God also repeated His promise to increase Abram's numbers greatly. Abram's response in this verse is entirely appropriate. He fell facedown before the Lord. Throughout history and in many cultures, this has been the ultimate expression of humility and submission. In one gesture, Abram communicated to God that he would receive all that God was saying with humility and great reverence. Although God does not require it of us, many believers today continue to approach God in prayer while kneeling or lying facedown on the ground.

Later, when God provides details on how He will accomplish His promises, Abram will once again fall on his face. At that point, however, it will be in laughter and disbelief. God's suggestion that a 99-year-old man and a barren, 89-year-old woman will have a child will be quite a shock (Genesis 17:17).