This verse is nestled in the context of Jesus’ instruction on forgiveness of one who has sinned against us. Was the issue faith or obedience? Does it take faith to be obedient? Jesus went on to talk about the “mulberry tree” (as an illustration of the sin of unforgiveness), whose roots are so strong it is practically impossible to uproot it. He told His apostles that they only needed the minutest portion of faith to dislodge it and cast it far away. And so it is with the sin of unforgiveness. No matter how long it has been rooted in our heart, when we exercise our faith by forgiving as Christ forgave us, this sin is totally removed. Selah.