Witnessing is a great aid to prayer. When we are faithful to witness to the lost God gives us power in prayer. In John 14:21 Jesus said, “He who has My commandments and keeps them, it is he who loves Me. And he who loves Me will be loved by My Father, and I will love him and manifest Myself to him.” I think a big part of His commandments spoken of here is to be His witnesses (Lu. 24:47-48; Acts 1:8). And so, when we are obedient to witness, He shows His love to us and manifests Himself to us, which of course gives us a good groundwork for prayer; for prayer is all about having a love relationship with God.
Also, in John 15:7 Jesus said, “If you abide in Me, and My words abide in you, you will ask what you desire, and it shall be done for you.” What does abide in Him mean? Basically it means to remain in Him. It means to be attached to Him and to draw life from Him. It also suggests that we love Him; and out of our love for Him we obey Him in everything, including witnessing. If we are faithful to abide in Him in this way, so that we are witnessing, then we have the promise of prayer. Yes, our witness is a great aid to prayer. In fact, without it our prayers would be quite powerless.