Psalms 44:2
How thou didst drive out the heathen with thy hand, and plantedst them; how thou didst afflict the people, and cast them out. How thou didst drive out the heathen with thy hand, and plantedst them; how thou didst afflict the people, and cast them out.
The verse looks back to how God with his own hand drove the heathen nations out of Canaan and planted his people in their place, afflicting those former inhabitants and casting them out. It presents the settlement of the promised land as God's own act, recalling his power over the peoples who had occupied it and his establishing of Israel there. This driving out and planting, afflicting and removing, was handed down by the fathers as the history that taught Israel received the land through God.
Possession did not come by Israel's own sword, strength, or military power, but by God's power and favor bringing victory and inheritance. The following verses make that contrast plain, that not their own arm but God's hand gave them the land. That remembrance gave David reason to trust God for present deliverance, since the same God who gave the land could save again.
The psalm to which the verse belongs is associated with the invasion of Sennacherib and the destruction of the Assyrian army in Hezekiah's reign. It belongs among the psalms meant to encourage the downcast, viewing Israel in a backslidden and persecuted condition. Paul quotes from this psalm in Romans 8 to point to victory through Christ even amid suffering.