This mode of speaking was often used by the saints, because God, when it pleased him to look on their miseries, was ever ready to bring them help. Nor were they words without meaning, when the faithful said, O Lord, thou hast seen; for they said this for their own sake, that they might shake off all unbelief. For as soon as any trial assails us, we imagine that God is turned away from us; and thus our flesh tempts us to despair. It is hence necessary that the faithful should in this respect struggle with themselves and feel assured that God has seen them. Though, then, human reason may say, that God does not see, but neglect and disregard his people, yet on the other hand, this doctrine ought to sustain them, it being certain that God does see them. This is the reason why David so often uses this mode of expression. Thou, Jehovah, he says, hast seen all their vengeances By vengeances here he means acts of violence, according to what we find in Psalm 8:2, where God is said "to put to flight the enemy and the avenger." By the avenger there he simply means, not such as retaliate wrongs, but cruel and violent men. So also, in this place, by vengeances, he means all kinds of cruelty, as also by thoughts he means wicked counsels, by which the ungodly sought to oppress the miserable and the innocent. He again repeats the same thing, --

Thou hast seen - all their imaginations - Every thing is open to the eye of God. Distressed soul! though thou knowest not what thy enemies meditate against thee; yet he who loves thee does, and will infallibly defeat all their plots, and save thee.

Thou hast seen all their vengeance,.... The spirit of revenge in them; their wrath and fury, and how they burn with a desire of doing mischief; as well as their revengeful actions, carriage, and behaviour:
and all their imaginations against me; their secret contrivances of mischief, their plots and schemes they devise to do hurt unto me.

imaginations--devices (Jeremiah 11:19).
Their vengeance--means their malice. Jeremiah gives his conduct, when plotted against by his foes, as an example how the Jews should bring their wrongs at the hands of the Chaldeans before God.

Seen - Thou hast been a witness to all their fury.