While the Lord Jesus was on the earth He was with twelve disciples, and He had a very intimate time with them. They lived together, they ate together, they walked together, and they worked together for three and a half years. The night He was betrayed He told them to their great surprise that He would leave and go away. He told them that if He did not go away He could not be in them. He had been incarnated, and He was among them. But this was not His goal, His destination. His goal was to enter into them. His destination was not to be among them but within them. He told them that He would go to the cross to be killed, but that He would ask the Father to give them another Comforter, the Spirit of reality (John 14:16-17). They had His physical presence temporarily among them and outside of them. But until He was crucified and resurrected, they did not have Him as their reality within them. He told them that if He went away, another Comforter would come who is the Spirit of reality. He would not only be with them but also in them. The Lord Jesus as the first Comforter could only be among them. What they needed was a second Comforter, actually just Himself as the Spirit of reality, to come and enter into them. He told them that His going away was His coming to be within them. He said, "I will not leave you orphans; I am coming to you" (John 14:18). He went on to say, "In that day you shall know that I am in My Father, and you in Me, and I in you." Verses 16 and 17 say that the Comforter, the Spirit of reality, will be in you, and verse 20 says that I will be in you. Are these two or one? No one can figure this out. In the Bible you do have the divine mathematics.
We all know that God the Spirit is one, uniquely one. But in the book of Revelation, God the Spirit is the seven Spirits (Rev. 4:5). Is God the Spirit seven or one? He is one-seven and seven-one. This is the divine mathematics. Don’t try to figure this out. This is why Martin Luther indicated that if you fully know the things concerning God, you must be God. We don’t know the things so clearly. They are too mysterious.
John 14:16-20 says that the second Comforter who is the Spirit of reality will come to be with them and in them. And the Lord said that His coming is My coming. So this means that the Lord Himself will come and be in them on the day of resurrection. On that day they would know that He was in the Father, and they were in Him. and He was in them. Then who is in whom? He was in the Father. They shouldn’t think that He was there without the Father. Even while He was with them, He was in the Father. But they were not in Him yet. On the day of resurrection they would know that He was in the Father and that they were in Him, and He was in them (v. 20). When they are in Him, they arc also in the Father, and He is in them. When He is in them. the Father also is in them. There is not only the coexistence among the Three of the Godhead, but also the coinherence. Each is in the other. I can testify that daily and hourly I experience this coinherence. I am living in my Lord, and He is in the Father) and He is also living in me. As He is living in me, the Father is also. Hallelujah! We all are in this mystery. This is for God’s expression.
(Concerning the Lord's Recovery, Chapter 4, by Witness Lee)