There is a whole theology of prayer in this remarkable event. Was it necessary for the servant to pray if Rebekah was already coming? Yes, for it is the will of God that we ask him in humble dependence for all that we need. Strictly speaking it is not necessary for us to ask, for God knows our needs even before we ask. It is not for his sake that we inform him of our needs, but for our sakes that we should learn that he is the provider of all things.
Furthermore, we see how our prayers fit into the plan of God. They may be regarded as one of a number of secondary causes that bring about the will of God. His will has been settled from before the creation of the world. Can we then influence the outcome of events by our prayers, or is all prayer futile because God has already decided what he is going to do? The answer of this passage and many other is that our prayers are included in the plan of God. Yes, they are no more necessary than any other secondary causes that God has chosen to use, and yet they form part of his eternal plan and without them the things that he has ordained would not come to pass. Our acts of will as free agents are included in that plan, therefore we ought to exercise that freedom to the full and ask for those things which are according to the will of God. We ought to pray fervently and frequently. God has promised to hear every prayer that is according to his will. From our perspective therefore we may see ourselves as contributing to the unfolding of God’s eternal plan as our desires become aligned with God’s desires and we ask what he is only too willing to grant.