John Newton penned three letters explaining his thoughts on how grace typically grows in the life of the Christian. Using agricultural terms he explains how grace develops in the sinner from the first green blade of conversion (A), to grace in the ear of corn (B), and then finally to mature Christian represented by corn ready for the harvest (C). In his letter explaining the highest levels of Christian maturity he writes this about humility and its fruits [Works, 1:212]:

A measure of this [humbling] grace, is to be expected in every true Christian: but it can only appear in proportion to the knowledge they have of Christ and of their own hearts. It is a part of C’s daily employment to look back upon the way by which the Lord has led him; and while he reviews the Ebenezers he has set up all along the road, he sees, in almost an equal number, the monuments of his own perverse returns, and how he has in a thousand instances rendered to the Lord evil for good. Comparing these things together, he can without affectation adopt the Apostle’s language, and style himself “less than the least of all saints” [Eph 3:8], and “of sinners the chief” [1 Tim. 1:15].