Galatians 3:15 - Promises on steroids?

"Brothers, according to man I am saying.  Yet [even] a covenant of man having been ratified, no one is rejecting or adding to."

-A covenant.  A covenant.  I don’t think that means what we think it means.  In fact we have a very dim idea of what it means.  The dictionary defines it simply as 'an agreement’.  And yet moderns have rather little reluctance to modify or otherwise abrogate "an agreement".  Our word is no longer our bond.  Anymore, you can’t take it to the bank, or to the store, or anyplace else, much less to a neighbor.

-Covenants were promises on steroids.  They were solemn oaths, inaugurated and ratified by death, a rather violent sacrifice and shedding of blood, the victim literally being cut into two and the covenanters passing between the two halves (this picture is plausibly where English gets the phrase, to cut a deal).  Nevertheless, a covenant, once ratified, was both irrevocable and unalterable.  Even when made under false pretenses, both parties were under obligation to respect the covenant (cf Joshua 9.22-23, 2Samuel 21.1).  Indeed, there were curses for breaking a covenant, as well as blessings for keeping it (thus we see the covenant between God and His people, the blessing for keeping the law and the curse for breaking it - Deuteronomy 11.26-28).  To Paul’s point tho, even on a strictly human level, modifying or altering a covenant was a no-no, inconceivable.  And so the implication then is that at a much higher level, there is not even the slightest chance of God ever breaking or otherwise altering any one of His promises.  And you can take that to the bank...