One of the things that is happening in the Lord’s-day worship service is that the church is conducting spiritual warfare. We see this throughout the book of Revelation, where it is the church’s songs and prayers that call forth God’s powerful action. We see it, too, in that God uses even the singing of babies to silence his enemies (Ps. 8:2 taken together with Matt. 21:16). Jesus prepares a table for his church in the very presence of her enemies (Ps. 23).
Thus, weekly communion: for when is the church not surrounded by enemies, and she must always find a table and an overflowing cup there.