I believe that God gives us a picture in Genesis 18 of our reluctance to preach the Gospel in a world who considers us ignorant, perhaps fanatical, but most of all irrelevant. In the text we find three men approaching Abraham’s camp. While the whole text implies a visit from the Lord God, the men are not identified until later as the Lord God (Genesis 18:22) and two angels (cp. Genesis 19:1). Abraham reacted to the visit with typical Middle Eastern hospitality (Genesis 18:1-2). He ran to meet them, bowing before them, and invited them to be his guests for a meal, resting from their journey while he washed their feet.
Certainly this wasn’t a chance meeting. The Lord didn’t merely stumble upon Abraham’s camp. He came there for a purpose, but what was that purpose? I believe the answer lies in the Covenant of Circumcision. This covenant was a covenant of intimacy with the Lord, and the Lord came to visit his friend. This very thing is something Abraham could expect of God under this new covenant. So, first of all this visit reaffirmed that promise of intimacy or the promise of friendship.A second purpose of the visit was to reaffirm the arrival of the promised heir—adding a time frame. For the first time Abraham was told exactly when the promised heir would appear.
Sarah was listening from her tent, and laughed within herself at the prospect of hearing that she would have a child within the year (Genesis 18:10-12). Isn’t it a little strange that the Lord questioned the reason for Sarah’s laughter (Genesis 18:13) but not the reason for Abraham’s laughter (Genesis 17:17)? I believe the answer lies in the fact that one expresses the joy of faith in God to bring such a thing about, while the other questions the possibility of its occurrence and expresses unbelief. Abraham believed God and this is evidenced in Genesis 17:18 as concern over Ishmael, but he couldn’t help but laugh at the whole idea of two old people giving birth to a son.
I believe Sarah’s laughter represents a third reason for God’s visit to Abraham. The Lord’s question in Genesis 18:13 implies Abraham is to be faulted for Sarah’s mocking laughter and unbelief. It may be that the whole prospect of Sarah becoming a mother at her age was so unbelievable that Abraham simply didn’t wish to be considered foolish for even mentioning it to Sarah. If Abraham told his wife of what God intended to do, she would have had time to consider what the Lord had already done for them and would have believed. If Abraham had evidenced his steadfast faith in the Lord’s promise, Sarah would have surely come to believe in the promise as well. Consequently, the Lord had to rebuke her unbelief (Genesis 18:13), because Isaac could only be received by faith (cp. James 1:5-8). Therefore, it was necessary for Sarah to believe the Lord could do this thing (cp. Genesis 18:14), because therein lay her strength to conceive (Hebrews 11:11).
Once we realize our failures it is necessary for us to admit them (Genesis 18:15). Sarah was afraid that the Lord would retract his promise (Genesis 18:15) and tried to deny that she laughed or mocked at his words, but such a thing is fruitless, for God knows our hearts (Psalm 139:1, 23); he knows the words on our tongue before we even utter them (Psalm 139:4). Nevertheless, our fears are out of place simply because God **is** Almighty (Genesis 17:1; cp. Genesis 18:14). If we are in unbelief, God won’t reject us because he will not deny himself (2Timothy 2:13). He is not a performance oriented God. God is interested in His own glory, not our mistakes. If his glory is evident, our behavior will change to image that glory (2Corinthians 3:18).
It seems that Abraham failed in expressing his faith in such a manner that others knew he depended upon God. God’s call to both intimacy and identification with him in the world often carries with it a measure of contempt from unbelievers. When are we apt to behave as Abraham did? – Abraham didn’t seem to have difficulty with the first covenant, because it was totally dependent upon God. But the 2nd covenant of circumcision or identification with God carries with it a heart relationship. We need to identify with God and our identity cannot be kept to ourselves. We need to let others see the choice we’ve made and understand that we belong to God.