"Faith is a living and unshakeable confidence, a belief in the grace of God so assured that a man would die a thousand deaths for its sake. This kind of confidence in God's grace, this sort of knowledge of it,. makes us joyful, high-spirited, and eager in our relations with God and will all mankind. That is what the Holy Spirit effects through faith."
— Martin Luther

(Can't forget the old school dudes like Martin Luther who laid the foundations of our faith through preaching and teaching! This quote taken from Martin Luther: Selections from His Writings.)

“Night and day I pondered until I saw the connection between the justice of God and the statement that ‘the just shall live by his faith.’ Then I grasped that the justice of God is that righteousness by which through grace and sheer mercy God justifies us through faith. Thereupon I felt myself reborn and to have gone through open doors into paradise.”
- Martin Luther, circa 1515

http://en.m.wikipedia.org/wiki/Martin_Luther