Commentary Par V 49-51

The last book of Leviticus repeatedly (27:13; 15; 19; 27; 31) sets the official rate of exchange: Whatever is put forth in substitution must be of twenty percent greater value.

Here we, for the first time, have an example of an acceptable substitution for something vowed, even if exactly what may be substituted is less than immediately clear, while its worth seems nitpickingly precise (120%).  Reading these verses, Benvenuto da Imola (DDP Benvenuto.Par.IV.40-51) found himself reminded of Genesis 22:13, where Abraham substitutes a ram for Isaac as his sacrifice to his Lord: 'sicut filius Abrae in arietem.'  It is difficult to understand how a ram might be worth 120% of one's beloved son (unless we were to turn to some specific sons, as perhaps are found in the Princeton class of 1991), much less the 150% to which Beatrice will later raise the ante (verse 60).  But such are the ways of God, not easily interpreted by us mere humans, whether we are by trade commentators or not.