With a view to the upcoming seminary Interim course on Heidelberg Catechism Preaching by Prof. B. Gritters (Jan.4-15, 2019), we offer a few choice quotations he supplied as a way to bring awareness to the course and to the ongoing need in Reformed churches to maintain (or return to) this practice.
From Zacharias Ursinus, one of the authors of the Catechism:
We do herewith affectionately admonish and enjoin upon every one of you, that you do, for the honour of God and our subjects, and also for the sake of your own soul’s profit and welfare, thankfully accept this proffered Catechism or course of instruction, and that you do diligently and faithfully represent and explain the same according to its true import, to the youth in our schools and churches, and also from the pulpit to the common people, that you teach, and act, and live in accordance with it, in the assured hope, that if our youth in early life are earnestly instructed and educated in the word of God, it will please Almighty God also to grant reformation of public and private morals, and temporal and eternal welfare” (Fred Klooster, The Heidelberg Catechism: Origin and History, 1995, 152)
From the Christian Reformed Church in 1920:
With a view to the dangers from without that threaten sound doctrine, and in consideration of the great need of, and the very meager interest in, the regular development of dogmatical truths, Synod emphasizes the time-honored custom of Catechism preaching, and the Classes are urged to give proper attention to this matter, that the regular consideration of the Catechism may be observed. (Quoted in The Church Order of the Christian Reformed Church As adopted by the Synod of 1920, W. Stuart and G. Hoeksema, Grand Rapids: Smitter Book Company, 65).
From the Church Order of the PRC (Article 68):
The ministers shall on Sunday explain briefly the sum of Christian doctrine comprehended in the Heidelberg Catechism, so that as much as possible the explanation shall be annually completed, according to the division of the catechism itself for that purpose.