On the Teacher's Task

Because God wishes the voice of teachers to sound forth in the church, as it is said concerning the ministry of the Gospel, Eph. 4:11, therefore the work of teaching is not undertaken in vain.
(Melancthon, Preface to the Loci)

The theologian's task is not to divert the ears with chatter, but to strengthen consciences by teaching things true, sure and profitable.
(Calvin, Institutes, 1.14.4)