Jeremiah 22:4

For if ye do this thing indeed, then shall there enter in by the gates of this house kings sitting upon the throne of David, riding in chariots and on horses, he, and his servants, and his people.

Cross-reference

Jeremiah 22:2 addresses the king sitting on David's throne, providing the immediate context for this conditional promise.

Jeremiah 17:25 uses nearly identical wording about kings entering gates, promising the same reward for obedience.