Adam Clarke Commentary on Genesis 20:16
http://www.sacred-texts.com/bib/cmt/clarke/gen020.htm http://www.godrules.net/library/clarke/clarkegen19.htm#16 * Behold, he is to thee a covering of the eyes - It - the one thousand shekels, (not he - Abraham), is to thee for a covering - to procure thee a veil to conceal thy beauty (unto all that are with thee, and with all other) from all thy own kindred and acquaintance, and from all strangers, that none, seeing thou art another mans wife; may covet thee on account of thy comeliness.
Sarah was the wife of Abraham, as well as being his half-sister, the daughter of his father Terah (Genesis 20:12).
