A Voice from the Past - Zwingli

That Christ is our justice, from which follows that our works in so far as they are good, so far they are of  Christ, but in so far as they are ours, they are neither right nor good.

Huldrich Zwingli, 1484-1531, XXII, Sixty Seven Articles of Zwingli.(Online Library of Liberty: Selected Works of Huldrich Zwingli, edited by Samuel Macauley Jackson, 1901, p.83)

Are our works only good so far as they are of Christ? What makes our works of Christ?