 Forbes became religiously puritanical and an avid preacher, though he was reluctant to enter the ministry.George Gledstanes, Archbishop of St Andrews, ordered him to enter the ministry or stop preaching, and as a result Forbes confined his preaching to his own household.At the death of his friend John Chalmers, the minister of Keith, in 1611, the dying Chalmers requested Forbes to take control of the parish of Keith and continue his work there.