Here is Charnock demonstrating his ignorance of the righteousness of God revealed in the gospel, and his ignorance of Christ as the end of the law for righteousness (cf. Romans 10:1-4). The SOLE CONDITION for salvation (Charnock's phrase is 'covenant of grace') is Christ's propitiating blood and imputed righteousness; His fulfillment of the PENAL and PRECEPTIVE demands of God's law and justice. God regenerates (saves) His people unconditionally, and an immediate and inevitable FRUIT (or RESULT) of that is FAITH. To CONFOUND or CONFUSE FRUITS with CONDITIONS of salvation is to CONFUSE salvation conditioned on Christ ALONE, with salvation CONDITIONED on the sinner (whether "graciously" enabled or not). Romans 11:6 is written PRECISELY against the type of doctrine that Charnock articulates in this quote.
Charnock on faith as a condition
"The covenant of grace doth NOT run, 'I will be your God, IF you will be my people; 'BUT 'I will be their God, and they SHALL be my people;' 'I will betroth thee to me forever; I will betroth thee to me forever; I will say, Thou art my people, and they shall say, Thou art my God.' His everlasting purpose is to write his laws in the hearts of the elect. He puts a CONDITION to his covenant of grace, the CONDITION OF FAITH, and he resolves to work that CONDITION in the hearts of the elect; and, therefore, believers have two immutable pillars for their support...these are election, or the standing counsel of God, and the covenant of grace. He will not revoke the covenant, and blot the names of his elect out of the book of life" (Stephen Charnock, Existence and Attributes of God). [Capital letter emphasis mine--CD.]