W.H. Carslaw, in his Six Martyrs of the Scottish Reformation, writes, "William Guthrie is frequently referred to as one of the first fruits of his (Samuel Rutherford's) ministry."

During his ministry at Fenwick, Ayrshire, from 1650 to 1664, one contemporary remarked that "he converted and confirmed many thousand souls, and was esteemed the greatest practical preacher in Scotland."

All of Guthrie's teaching and pastoral experience were poured into this work, his only book. The remarkable fact that it has gone through more than eighty editions and been translated into several languages testifies to its value.

Pulling a copy of Guthrie's book from his pocket, John Owen declared "That author I take to have been one of the greatest divines that ever wrote." Furthermore, concerning this great treasure, Owen also proclaimed that "there was more divinity in that volume than in all his own works" (Antithesis II:4, p. 15).

Thomas Chalmers described it as "the best book I ever read." It was written, its author says, for those who "have neither much money to spend upon books, not much time to spare in reading." It describes in a simple, clear and attractive style what it means to be a Christian, and how to become one.

Guthrie was a master spiritual physician, and his wisdom appears on every page of this outstanding work (adapted from the back cover). Chapter four is especially interesting in that it deals with "Personal Covenanting With God in Christ."