“By what authority are you doing these things?” they asked. “And who gave you authority to do this?” (Mk. 11:28)
The chief priests were telling Jesus, "Who do you think you are?" or "What gives you the right to come in here and act like this?"
Little did they know (or care, really) about the single, driving principle of His life: "I do as the Father has commanded me, so that the world may know that I love the Father..." (Jn. 14:31). There was never a moment in His life when He acted without the authority of His Heavenly Father.
Christians should have that same desire as the Master, indeed we must: "Whatever you do in word or deed, do everything in the name of the Lord Jesus, giving thanks through Him to God the Father" (Col. 3:17). Whatever it is you happen to be doing or saying or thinking, if it is without His approval, it is sin.
Honest Bible students recognize the implications of this, and really do care about the authority of Christ. We all swing and miss, but true believers actually care when they miss and won't take their bat to the head of the man who points it out.
One fella got so worked up he said, "You church-of-christers are always carryin' on about authority, when there's plenty you don't have authority for--church buildings, hymnals, communion trays, and the like. Where'd you find authority for that?"
Well I can't speak for "church-of-christers" (whoever they are), I can only speak for myself as a Christian.
When Jesus gives a command, inherit within that command is the authority for the means to accomplish it.
For example: "Go, therefore, and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit..." (Matt. 28:19). In giving this command to "go and make disciples," Jesus didn't say specifically to walk, ride, sail, or use any other means--in other words, the means of going is up to us! These days we can even fly across oceans!
At any rate, the same is true regarding the command "do not forsake assembling together" (Heb. 10:24-25), or coming "together as a church" "on the first day of each week" (1 Cor. 11:18; 16:1-2).
Since the Lord commands/authorizes His people to assemble (and engage in acts of worship while assembled)--singing praises and partaking of the Lord's Supper, these commands presuppose whatever is necessary to accomplish them.
If we're going to come together as a (local) church, there be a place to do that. In the first century Christians gathered in...
...Solomon’s Colonnade (Acts 5:12)
...the School of Tyrannus (Acts 19:9)
...an upper room with many flickering lamps (Acts 20:8)
...members' homes (Rom. 16:5; 1 Cor. 16:19)
all sorts of places, really, but the point is they recognized the need to do this. True, the specifics (regarding the type of building, decor, etc.) are matters of judgment, and it's also true that Christians can and have used very poor judgment in such matters. BUT it is NOT true that procuring a place to assemble for worship is "without" authority.
Such is no more without authority than using hymnals to facilitate singing hymns is without authority. Do we have to have hymnals? Of course not, but purchasing and using them is authorized because the command to sing and make melody in your heart to the Lord authorizes their use (Eph. 5:19).
It's important to remember in these discussions that nothing can be lawfully used to fulfill the Lord's command that is not first authorized (1 Cor. 6:12). Meaning if He never gave us the command to assemble, then procuring a place to assemble would facilitate something He never authorized us to do.
Neither can a use a means which violates some other command He's given. That is, I can't steal a car in the "Name of the Lord" so I can go and preach somewhere. That might sound absurd, but you run into some absurd reasoning out there. There was once a local prostitution ring that identified as "Christian"--not kidding. Insert facepalm emoji here.
Often sin is not the failure to discern between what is right and wrong, but a failure to discern between what is right and almost right.
In a similar vein, the command to sing and make melody in my heart to the Lord cannot authorize the use of a piano (or any other mechanical instrument) because pianos facilitate the playing of music in worship--something He never authorized in the New Testament.
Expediencies cannot place us outside of God's laws, then they are no longer expedient, but sinful. Actions must first be authorized, then we may choose to restrict our lawful choices for the greater good--this is expedience.
We have authority to teach, and Shepherds must feed the flock among them (Eph. 4:11; 1 Pet. 5:2). Dividing up into Bible classes is an expedience in fulfilling these commands.
Laying by in store n the first day of each week as a church is authorized in 1 Cor. 16:1-2. Using collection baskets to gather the funds during worship is an expedience.
Baptism is commanded for the forgiveness of sins in Acts 2:38. Having a baptistery as a ready water source is an expedience.
In each case, we could argue that there are many ways to fulfill the commands given. Not every possible method of fulfillment is necessarily the best method to use in a given place or time, and God puts us on our honor with many things.
A rapidly growing church might find their place of assembly too restrictive for their growing membership. Another church might find renting too much of a drain on the budget.
Each congregation must act with wisdom in accordance with the Lord's will.