Jesus said in Matthew 18:20 (NASB) “For where two or three have gathered together in My name, there I am in their midst.”
The scriptures give us insight of His spiritual presence at the calling upon of His name when He later sent out the 70 disciples with the same authority He had given the apostles.
Luke 10:17 (NASB) says ... And the seventy returned with joy, saying, "Lord, even the demons are subject to us in Your name.” To which Jesus immediately responded (verse 18 Youngs Literal Translation) "I was beholding the Adversary, as lightning from the heaven having fallen."
Jesus is here using the way lightning flashes in the sky as an analogy of how His spiritual presence was called to the site of the disciples at the calling upon of His name and thus it was He Himself who confronted the demon. It is not saying that Satan was cast out of heaven at this time.
This understanding of how this incident is a testimony of His spiritual presence being invoked at the calling upon of His name remains hidden from most to this very day, it is a phenomenon which He attests to in Luke 10:21 (NASB) which reads.... At that very time He rejoiced greatly in the Holy Spirit, and said, “I praise Thee, O Father, Lord of heaven and earth, that Thou didst hide these things from the wise and intelligent and didst reveal them to babes. Yes, Father, for thus it was well-pleasing in Thy sight.
This is a hidden gem in the scriptures but there is also another underlying hidden gem in this story that is found in the answer to the question "Why did He not also grant them authority at this time to baptize in His name?"
The answer is that during the Lord's earthly ministry every baptism was performed in His physical presence with Him acting in the official capacity of bearing witness the baptism for the remission of sin.
Since He was standing right there in the flesh it was not necessary to call upon His name as an invocation of His presence to witness the baptism during His earthly ministry. And thus the revelation of calling upon of the Name for the Lord's spiritual presence remained hidden until the Day of Pentecost.
It was His choice that this should remain a hidden gem until the time He had appointed when (as promised) by the mouth of Peter the "keys to the kingdom of heaven" were unveiled when he said "Repent and be baptized in the Name of Jesus Christ for the remission of sins, and you shall receive the gift of the Holy Spirit."