Thou hast set a bound that they may not pass over; that they turn not again to cover the earth.
Psalm 104:9 KJV
God is speaking here of the sea that covered the mountains, the said sea which retreated after his rebuke (see verses 6-7). After their retreat, he sets a boundary that prevents them from being able to once more cover the mountains. Yes I said “them” in reference to the sea, cause it speaks to the forces darkness.
The Word of God i.e. Jesus chased them from you, from your earthen vessel and he himself is the boundary that prevents the sea from being able to overtake/cover you (earthen man) as they did in times past. He is the stronger man that now guards your house. He is the standard God lifts that limits the flood/the enemy.
Without him, the sea will overtake the earth i.e. darkness will overtake us earthen men.