Jesus taught that prayer should be in unity with others (Matthew 18:19-20)
Sometimes when we pray we are not in unity and in agreement with others. But we should always strive for unity—that is, unity in the body of Christ. We can never have unity and agreement with those outside of the body of Christ, but we should always strive for unity within the body. For the body of Christ is one, of which we are all part. Therefore, since each of us (in the Christian church) is a part for the body of Christ it is natural that our prayers should be united and flow together in agreement by the power of the Holy Spirit.
At first it was hard for me to find in the gospels where Jesus taught this idea of unity in prayer (other then in Matthew 18:19-20); but then, as I studied it, it exploded right before me. I found that Jesus taught unity in prayer in all of his teachings on prayer.
In John 17:22-23 we see that Jesus prayed for unity—that all believers might be one, just as He was one with His Father.
Secondly, Jesus taught unity in prayer every time He spoke of abiding in Him and of praying in His name. And the reason I say that is because when He said to His disciples, “If you ask anything in My name…” (Jn. 14:14), and “If you abide in Me…” (Jn. 15:7), and “whatever you ask the Father in My name…” (Jn. 15:16), He was not just speaking of prayer for one person (isolated from others), or for one disciple at a time, He was talking about united prayer—prayer with and for all of His disciples together, and really for all of us too. We see this plainly from the way it naturally reads; but we also pick it up from the Greek. For the terms “you shall ask,” and “if you abide,” are written in the second person plural, which may be rendered “you-all,” or “all of you.”
We also see His teaching on unity in prayer in the example prayer He gave to His disciples (Matt. 6:9-16). Here, when He said, “Our Father” (instead of “my Father”), He was teaching that we should pray together as a family. So whenever anyone (any individual) prays, he should recognize that he is one with the body of Christ, and so he should pray with that idea in mind.
In Matthew 18:19-20 Jesus teaches on group prayer. It seems that Jesus is teaching here that there is a special power in group prayer. For He taught that when we pray in a group and ask in His name (which means to pray according to His will) three things will occur: (1) we will agree together, (2) He will be there in our midst, and (3) we will receive whatever we ask for.