Brothers, let me put this in human terms. Even a human covenant, once it is ratified, cannot be canceled or amended.
Textus Receptus (TR) - Galatians 3:15 >Ἀδελφοί, κατὰ ἄνθρωπον λέγω· ὅμως ἀνθρώπου κεκυρωμένην διαθήκην οὐδεὶς ἀθετεῖ ἢ ἐπιδιατάσσεται.