Discovering bitter water at Marah was a devastating experience for the Israelites after their deliverance from Egypt. They were totally unprepared for it. We may have 'bitter pool' experiences too - disillusionment, business failure, broken relationships, a health breakdown etc. God will often use these to test and strengthen us. Derek Prince explains God's purpose in testing and how to respond. Complaining will produce nothing; persevering in faith will bring a deeper revelation of Himself. Often man's disappointment are God's appointments - but we can only discover His purposes in them as we respond in faith.