Conversion, then, is repentance (turning from sin and unbelief) and faith (trusting in Christ alone for salvation). They are really two sides of the same coin. One side is tails – turn tail on the fruits of unbelief. The other side is heads – head straight for Jesus and trust His promises. You can’t have the one without the other any more than you can face two ways at once, or serve two masters.
John Piper