Adam Clarke on Hosea 10:4

They have spoken words - Vain, empty, deceitful words.

Swearing falsely - This refers to the alliances made with strange powers, to whom they promised fidelity without intending to be faithful; and from whom they promised themselves protection and support, notwithstanding God was against them, and they knew it. All their words were vain, and in the end as bitter as gall.

Judgment springeth up as hemlock - As our land lies without cultivation, so that we have nothing but noxious weeds instead of crops; so we have no administration of justice. What is done in this way is a perversion of law, and is as hurtful to society as hemlock would be to animal life. All this may refer to the anarchy that was in the kingdom of Israel before Hoshea's reign, and which lasted, according to Archbishop Usher, nine years. They then, literally, "had no king."