THE WORD OF GOD IS A MOST PRECIOUS TREASURE.
For the Word of God is the sanctuary above all sanctuaries, yea, the only one which we Christians know and have. For though we had the bones of all the saints or all holy and consecrated garments upon a heap, still that would help us nothing; for all that is a dead thing which can sanctify nobody. But God’s Word is the treasure which sanctifies everything, and by which even all the saints themselves were sanctified. At whatever hour, then, God’s Word is taught, preached, heard, read or meditated upon, there the person, day, and work are sanctified thereby, not because of the external work, but because of the Word, which makes saints of us all. Therefore I constantly say that all our life and work must be ordered according to God’s Word, if it is to be God-pleasing or holy. Where this is done, this commandment is in force and being fulfilled. On the contrary, any observance or work that is practiced without God’s Word is unholy before God, no matter how brilliantly it may shine, even though it be covered with relics, such as the fictitious spiritual orders, which know nothing of God’s Word and seek holiness in their own works.
WE MUST NOT ONLY HEAR THE WORD, BUT ALSO KEEP IT.
Therefore not only those sin against this commandment who grossly misuse and desecrate the holy day, as those who on account of their greed or frivolity neglect to hear God’s Word or lie in taverns and are dead drunk like swine; but also that other crowd, who listen to God’s Word as to any other trifle, and only from custom come to preaching, and go away again, and at the end of the year know as little of it as at the beginning. For hitherto the opinion prevailed that you had properly hallowed Sunday when you had heard a mass or the Gospel read; but no one cared for God’s Word, as also no one taught it. Now, while we have God’s Word, we nevertheless do not correct the abuse; we suffer ourselves to be preached to and admonished, but we listen without seriousness and care. Know, therefore, that you must be concerned not only about hearing, but also about learning and retaining it in memory, and do not think that it is optional with you or of no great importance, but that it is God’s commandment, who will require of you how you have heard, learned, and honored His Word.
Luther’s Large Catechism, Third Commandment