This is a quote from the Large Catechism where Martin Luther addresses the frequency of holy communion:
[T]here is indeed need for some admonition and exhortation, that men may not let so great a treasure which is daily administered and distributed among Christians – pass by unheeded, that is, that those who would be Christians make ready to receive this venerable Sacrament often. For we see that men seem weary and lazy with respect to it . . .
Some pretend that it is a matter of liberty and not necessary, and that it is sufficient to believe without it; and thus for the most part they go so far that they become quite brutish, and finally despise both the Sacrament and the Word of God. . .
And we have, in the first place, the clear text in the very words of Christ: “Do this in remembrance of me.” These are bidding and commanding words by which all who would be Christians are enjoined to partake of this Sacrament. Therefore, whoever would be a disciple of Christ, with whom He here speaks, must also consider and observe this, not from compulsion, as being forced by men, but in obedience to the Lord Jesus Christ, and to please Him. However, if you say: “But the words are added, ‘As oft as ye do it;’ there He compels no one, but leaves it to our free choice,” I answer, “That is true, yet it is not written that we should never do so. Yea, just because He speaks the words ‘As oft as ye do it,’ it is nevertheless implied that we should do it often”
– Dr. Martin Luther (Large Catechism, The Sacrament of the Altar; paragraphs 39-47).