"The Lord is an eternal rock". The Bible speaks in very concrete terms. God is a source of strength. God is utterly reliable and faithful. God is a firm place in the shifting sands of life and the swampy places of doubt and indecision. All of these more abstract terms are summed in the image of a rock. One scholar suggests particularly that it is an image of the Resurrection. Death is like a swamp, into which we sink. But we will not sink into death forever since our feet will, as it were, touch rock bottom and we will find ourselves resting on God, who is our life and our hope and our strength.

Jesus hints at the same image when He encourages us to build our house on rock and not on sand. God has to be the foundation of our life, otherwise we will easily fall. So Jesus tells us how we build our lives on God, namely by keeping His words. St Paul will later on develop this same image, reminding us that we must build our lives on the only foundation there is, the foundation which is Christ.