My introduction to Puritan theology in seminary was the study of William Ames' The Marrow of Theology. I read again his comments on faith (in light of a recent sermon on the Sabbath commandment) and found them so helpful...
1. Faith is the resting of the heart on God, the author of life and eternal salvation, so that we may be saved from all evil through Him and may follow all good. Isaiah 10:20, "Lean upon the Lord, the Holy One of Israel, in faith..."
11. Faith is the virtue by which, clinging-to the faithfulness of God, we lean upon him, so that we may obtain what he gives to us. John 3:33, He who receives his testimony has sealed that God is true; John 1:12, As many as received him believed in his name.
12. These five things belong together in divine faith: 1) a knowledge of what God testifies to; 2) a pious affection toward God which gives his testimony greatest force with us; 3) an assent given to the truth testified to, because of this affection toward God who is the witness of it; 4) a resting upon God for the receiving of what is given; and 5) the choosing or apprehension of what is made available to us in the testimony.