“worthless offerings.” The priests and people were wicked and unrepentant, so their offerings were worthless. Offerings and sacrifices were never designed to make a person with an evil heart acceptable in the sight of God. Isaiah 1:10-19 is all about what God wants and what He doesn’t want from Israel. [For more information about the sacrifices of wicked people being of no value, see commentary on Amos 5:22.]
“New moons.” The beginning of each month, the new moon, was celebrated by special offerings and blowing of trumpets (Num. 10:10, 28:11-15; see commentary on Num. 28:11). In time, the Jews turned the new moon into a feast day (1 Sam. 20:5).