Adam Clarke on Isaiah 30:1

And that cover with a covering "Who ratify covenants" - Hebrews "Who pour out a libation." Sacrifice and libation were ceremonies constantly used, in ancient times by most nations in the ratifying of covenants: a libation therefore is used for a covenant, as in Greek the word σπονδη, for the same reason, stands for both. This seems to be the most easy explication of the Hebrew phrase, and it has the authority of the Septuagint, εποιησατε συνθηκας.