And Abraham said of Sarah his wife, {b} She is my sister: and Abimelech king of Gerar sent, and took Sarah.

(b) Abraham had now twice fallen into this sin: such is man's frailty.Genesis 20:2 Parallel Commentaries

And to Holy David Indeed it Might More Justly be Said...
22. And to holy David indeed it might more justly be said, that he ought not to have been angry; no, not with one however ungrateful and rendering evil for good; yet if, as man, anger did steal over him, he ought not to have let it so prevail, that he should swear to do a thing which either by giving way to his rage he should do, or by breaking his oath leave undone. But to the other, set as he was amid the libidinous frenzy of the Sodomites, who would dare to say, "Although thy guests in thine own …
St. Augustine—Against Lying

The Interpretation of the Early Narratives of the Old Testament
[Sidenote: Importance of regarding each story as a unit] Of all the different groups of writings in the Old Testament, undoubtedly the early narratives found in the first seven books present the most perplexing problems. This is primarily due to the fact that they have been subject to a long process of editorial revision by which stories, some very old and others very late and written from a very different point of view, have been closely joined together. While there is a distinct aim and unity …
Charles Foster Kent—The Origin & Permanent Value of the Old Testament