Martin Luther from the preface to his large catechism (my emphasis):
I must still read and study daily, and yet I cannot master it as I wish, but must remain a child and pupil of the Catechism, and am glad so to remain… Therefore I beg such lazy paunches or presumptuous saints to be persuaded and believe for God’s sake that they are verily (verily!) not so learned or such great doctors as they imagine; and never to presume that they have finished learning [the parts of the Catechism] …. For though they should know and understand it perfectly (which, however, is impossible in this life), yet there are manifold benefits and fruits still to be obtained, if it be daily read and practised in thought and speech.
This great saint admitted his need to regularly study the very catechism he had written! And yet how few Christians (this one included) know anything of them, much less find themselves able to quote them? I for one am resolving to spend more time, regular time, reading and rereading and these great writings (examples: Westminster Confession and Shorter / Larger Catechisms with Scripture proofs, Lutheran Book of Concord). For what are they but the wise summary of Scriptural truths that all Christians should know?