John Knox's Only Written Sermon - A Sermon on Isaiah 23:13-21, Preached in St. Giles's Church, Edinburgh, 19th August 1565 was formerly titled "A Sermon on Isaiah 23:13-21, Preached in St. Giles's Church, Edinburgh, 19th August 1565."

In the preface to this sermon John Knox writes: "Wonder not, Christian reader, that of all my study and travail within the Scriptures of God these twenty years I have set forth nothing in expounding any portion of Scripture except this only rude and indigested sermon, preached by me in the public audience of the Church of Edinburgh the day of the year above mentioned. That I did not, in writing, communicate my judgment upon the Scriptures, I have ever thought and yet think myself rather called of my God to instruct the ignorant, comfort the sorrowful, encourage the weak, and rebuke the proud, by tongue and lively voice, in these most corrupt days, than to compose books for the age to come, seeing that so much is written, and that by men of the most singular condition, and yet so little observed, I decreed to contain myself within the bounds of that vocation whereunto I found myself especially called" (cf. Reed's, John Knox the Forgotten Reformer, p. 35).

Stalker, in John Knox: His Ideas and Ideals continues, "In spite, however, of this modest disclaimer, Knox is a fairly voluminous author; his works, in the classical edition of David Laing, filling six considerable volumes. Many of them were, indeed, so occasional, called forth by the demands of the hour, that he may hardly have though of them as serious efforts at literature; but the character thus impressed upon them -- of casts taken straight from events -- lends to them for posterity a peculiar value; and, together, they at the same time afford a tolerably sufficient image of the author's mind."