Genesis 20 presents us with a familiar pattern: Abraham lies about Sarah’s identity as his wife. In doing so, he jeopardizes two covenants at once.
First, Abraham jeopardizes his marriage covenant. To save his own skin from a perceived, not an actual threat, he lies: “She is my sister” (v.2). In the process, he leaves his bride utterly exposed to exploitation by Abimelech. The only reason she isn’t ultimately violated is that the Lord Himself personally intervenes through Abimelech’s dream (vv.3–7). It would be one thing, I suppose, for Abraham to have lied about Sarah’s identity to make her safer: to expose himself to danger so that he might insulate her. But in fact he does precisely the opposite: he lies about Sarah to make himself safer, and by so doing exposes her to great moral and physical danger.
By comparison to his greatest son, Abraham is a poor specimen of a husband indeed: “Husbands, love your wives, as Christ loved the church and gave Himself up for her, that He might sanctify her, having cleansed her by the washing of water with the word, so that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish. In the same way husbands should love their wives as their own bodies….” (Ephesians 5:25-28). Abraham gave Sarah up for himself, and did not guard her purity.
The second covenant Abraham puts into jeopardy is the Lord’s covenant with him. The Lord had promised that Abraham & Sarah would be given a son (Chs.17-18). Abraham’s deception in Ch.20 raises the possibility that, if Sarah becomes pregnant, it would appear that Abimelech, rather than Abraham, was the father, thus casting a shadow of uncertainty over the heart of the Lord’s covenant with Abraham.
But the Lord intervenes to protect, not merely Sarah’s purity, but the integrity of His covenant with Abraham. Again and again throughout Genesis, the treasure of the covenant is placed into hands that are not sufficiently faithful to guard it well. The only hope is always that the Lord’s own zeal to uphold the covenant exceeds man’s that it be upheld.
This is the plotline of the entire Bible. This the plotline of history. This is the story of the Christian life: it is He who began a good work in us, who will also be the One to bring it to completion in the day of Christ Jesus (Philippians 1:6).