John Wesley on Hebrews 12:22

But ye - Who believe in Christ. Are come - The apostle does not here speak of their coming to the church militant, but of that glorious privilege of New Testament believers, their communion with the church triumphant. But this is far more apparent to the eyes of celestial spirits than to ours which are yet veiled. St. Paul here shows an excellent knowledge of the heavenly economy, worthy of him who had been caught up into the third heaven. To mount Sion - A spiritual mountain. To the city of the living God, the heavenly Jerusalem - All these glorious titles belong to the New Testament church. And to an innumerable company - Including all that are afterwards mentioned.