Recently a friend asked me why we should go to church every Sunday. I told him to learn the Word of God, but he said we can learn that any time. So why should we go to church?
Ask your friend what he learned from the Bible last week on his own. Most likely he will admit that he hadn't had time to study last week. Then tell him the topics of the lessons you learned in the last week at church.
I teach college classes once in a while. The class I'm teaching this quarter is one that is offered on-line as well as in a classroom setting. I was surprised how many told me that they tried to take the on-line class but found out that they just couldn't learn the material. Without scheduled class times, it was too easy to put things off. Without a teacher to point out the important parts of the material, it was too easy to skip around or only "learn" what they basically already knew. Without a class to interact with, it was easy to miss the "obvious" questions that should have been addressed.
"And let us consider one another in order to stir up love and good works, not forsaking the assembling of ourselves together, as is the manner of some, but exhorting one another, and so much the more as you see the Day approaching" (Hebrews 10:25).
Church is a time for people who have the same attitudes toward God to gather together and share their beliefs and knowledge. I can't recall how many people have told me that going to church is like recharging their spiritual batteries. It is the interaction that does this. As the Proverb says, we are iron sharpening iron (Proverbs 27:17).
There are going to be times you will be dragging spiritually and a brother will ask you what is wrong and then tell you things from his own life and what he knows from the Bible that will give you a new direction to your life. There will be other times that you will do it from some other brother. "Two are better than one, Because they have a good reward for their labor. For if they fall, one will lift up his companion. But woe to him who is alone when he falls, For he has no one to help him up. Again, if two lie down together, they will keep warm; But how can one be warm alone? Though one may be overpowered by another, two can withstand him. And a threefold cord is not quickly broken" (Ecclesiastes 4:9-12).
Growth cannot come on your own. God knows that and that is why He designed the church as He did. "And He Himself gave some to be apostles, some prophets, some evangelists, and some pastors and teachers, for the equipping of the saints for the work of ministry, for the edifying of the body of Christ, till we all come to the unity of the faith and of the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ; that we should no longer be children, tossed to and fro and carried about with every wind of doctrine, by the trickery of men, in the cunning craftiness of deceitful plotting, but, speaking the truth in love, may grow up in all things into Him who is the head--Christ-- from whom the whole body, joined and knit together by what every joint supplies, according to the effective working by which every part does its share, causes growth of the body for the edifying of itself in love" (Ephesians 4:11-16).
Your friend, on his own, has no fellowship with believers. He has no support system to watch over him and to help him when he stumbles. He has no motivation to study more or study harder. And worse of all, he is failing to worship the very God he claims to believe in. Jesus promised, "For where two or three are gathered together in My name, I am there in the midst of them" (Matthew 18:20). If your friend knew that Jesus was going to be physically present with the church next Sunday, would he be there? Most likely the building would not be able to hold all the people who would be eagerly seeking the Lord. Yet our Lord is with His church each and every gathering and many won't bother to give Him a portion of their time.
Worship cannot be fully done on your own. "The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ? For we, though many, are one bread and one body; for we all partake of that one bread" (I Corinthians 10:16-17). You cannot partake of the Lord's Supper on your own. You cannot share the memory of the Lord's death when you are by yourself. And when you are alone, you can't even claim to be sharing it with the Lord.
"Speaking to one another in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord, giving thanks always for all things to God the Father in the name of our Lord Jesus Christ, submitting to one another in the fear of God" (Ephesians 5:19-21). How do you sing and submit to one another when you are all alone? You can't.
"For in fact the body is not one member but many" (I Corinthians 12:14). A person cannot truly claim to be Christian, a part of the body of Christ, by not interacting with the rest of the body. "There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus" (Galatians 3:28). If your friend wants to get to heaven, then he needs to start being obedient to his Lord's commands and worship the Lord with his fellow Christians. Otherwise, the joy of the gathering of the saints in heaven won't be awaiting him. He lives a lonely life on earth and lonesome misery in the life to come.