John Calvin on Genesis 21:23

23. That thou wilt not deal falsely with me “Si mentitus fueris mihi.” — “If thou shalt have lied unto me.” In the margin Calvin gives, “Si fefelleris, aut infideliter egeris.” — “If thou shalt have deceived, or have acted unfaithfully.” See margin of English version. — Ed Literally it is, ‘If thou shalt lie;’ for, among the Hebrews, a defective form of speech is common in taking oaths, which is to be thus explained: ‘If thou shouldst break the promise given to me, we call upon God to sit as Judge between us, and to show himself the avenger of perjury.’ But ‘to lie,’ some here take for dealing unjustly and fraudulently; others for failing in the conditions of the covenant. I simply understand it as if it were said, ‘Thou shalt do nothing perfidiously with me or with my descendants.’ Abimelech also enumerates his own acts of kindness, the lore effectually to exhort Abraham to exercise good faith; for, seeing he had been humanely treated, Abimelech declares it would be an act of base ingratitude if he did not, in return, endeavor to repay the benefits he had received. The Hebrew word חסד( chesed ) signifies to deal gently or kindly with any one. “Secundum misericordiam quam feci tecum facies mecum,” is Calvin’s version; and the comment is, “Misericordiam facere cum aliquo Hebraeis significat clementer et benigne eum tractare.” — Ed For Abimelech did not come to implore compassion of Abraham, but rather to assert his own royal authority, as will appear from the context.