This verse is often cited as an incentive to regular church attendance, but it can also relate just as well to any gathering of two or more believers in Christ’s name. The Lord Jesus said: "For where two or three are gathered together in my name, there am I in the midst of them" (Matthew 18:20).
It is fascinating to note that the Greek word translated "assembling together" in this verse is used only one other time in the New Testament, and there it is translated "gathering together." "Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him" (2 Thessalonians 2:1).
In this verse, Paul was reminding the Thessalonians of his previous letter to them, in which he had written about the return of Christ and the gathering together of all believers to meet Him in the air (1 Thessalonians 4:15-17). Perhaps the writer of our text verse, since he was using the same unique terminology, was referring to the same event.
That is, whenever there is an assembling together of believers, it is in a sense a little preview of that great gathering in the skies when Christ returns, as we exhort one another to "look for him" (Hebrews 9:28), and so much the more, as we see the day approaching.
Since our text verse does not actually mention the church by name, it seems to apply to any assembling of believers. However, there is one very significant use of "church" in Hebrews, and it refers specifically to the coming meeting in the air, where we shall all gather at "the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect" (Hebrews 12:23). HMM