Nouns that present a verbal implication may be followed by a genitive
case, called an objective genitive. Faith is active, and in Mark 11:22,
God is the object of faith. So, the translation should be "Have faith
in God."
I am aware of other options, but this is my understanding of the verse.
-- Lee R. Martin Part-Time Instructor in Hebrew and Biblical Studies Church of God Theological Seminary Cleveland, TN 37311 Pastor, Prospect Church of God