Isaiah 1:4 - Matthew Poole's English Annotations on the Holy Bible

Ah: this particle implies both his wonder, and anger, and grief, and shame that they were such. Laden with iniquity, Heb. of heaviness of iniquity, i.e. of heavy or great sins; for heavy is commonly put for great or grievous, as Isaiah 21:15, Isaiah 30:27. Laden not with the sense of sin, as Matthew 11:28, but with the guilt and bondage of sin. A seed of evil-doers; the children of wicked parents, whose guilt they inherit, and whose evil example they follow. That are corrupters, Heb. that corrupt, to wit, themselves, or their ways, or others by their counsel and example. Or, that destroy themselves and their land by their wickedness. They have forsaken the Lord, not in profession, but in practice and reality, neglecting or corrupting his worship, refusing his yoke and conduct. They have provoked the Holy One of Israel unto anger; they have lived as if it were their great design and business to provoke him. They are gone away backward; instead of proceeding forward, and growing in grace, which was their duty, they are all fallen from their former professions, and grown worse and worse, and have impudently turned their backs upon me.