Charles Ellicott Commentary Isaiah 65:7

"your own iniquities, and the iniquities of your fathers together, saith Jehovah, that have burned incense upon the mountains, and blasphemed me upon the hills; therefore will I first measure their work into their bosom." — Isaiah 65:7 (ASV)

Which have burned incense upon the mountains ... —The old deep-rooted sin of the worship of high places (Hosea 4:13; Ezekiel 6:13; 2 Kings 15:4; 2 Kings 15:35). The worship paid there to other gods, or nominally to Jehovah in a way which He had forbidden, was practically a “blasphemy” or “reproach” against Him.

Their former work. —Better, I will measure their work first into their bosoms. That was, so to speak, the primary duty of the Supreme Ruler.