Charles H. Spurgeon on Psalms 79:6

Neglect of prayer by unbelievers is threatened with punishment. The prophet's imprecation is the same in effect with a threatening, see Jer 10:25, and same imprecation, Ps 79:6. The prophets would not have used such an imprecation against those that call not upon God, but that their neglect of calling on his name makes them liable to his wrath and fury; and no neglect makes men liable to the wrath of God but the neglect of duty. Prayer, then, is a duty even to the heathen, the neglect of which provokes him to pour out his fury on them.—David Clarkson.