Jamieson, Fausset and Brown on Isaiah 1:4

4. people--the peculiar designation of God's elect nation (Ho 1:10), that they should be "laden with iniquity" is therefore the more monstrous. Sin is a load (Psa 38:4; Mt 11:28).

seed--another appellation of God's elect (Ge 12:7; Jr 2:21), designed to be a "holy seed" (Is 6:13), but, awful to say, "evildoers!"

children--by adoption (Ho 11:1), yet "evildoers"; not only so, but "corrupters" of others (Ge 6:12); the climax. So "nation--people--seed children."

provoked--literally, "despised," namely, so as to provoke (Pr 1:30, 31).

Holy One of Israel--the peculiar heinousness of their sin, that it was against their God (Am 3:2).

gone ... backward--literally, "estranged" (Psa 58:3).