John Gill 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)

Your iniquities, and the iniquities of your fathers together
(says the Lord)
That is, the punishment both of the one and of the other; these being alike, and continued from father to son, and approved of, and committed by one generation after another, till the measure was filled up; and then the recompence of reward is given for all of them together at once: which have burnt incense upon the mountains, and blasphemed me upon the hills; where they offered incense and other sacrifices to idols, which was interpreted by the Lord as a blaspheming and reproaching of him; see (Isaiah 57:7) (Jeremiah 2:20) (3:6) : therefore will I measure their former work into their bosom ;
punish them for their former sins as well as their latter ones, and both together.