In John 14:12 Jesus said, "He that believes on me, the works I do shall he do also, and greater works than these shall he do." Could these two beliefs in Jesus be connected somehow?
We are talking about sacrifice. You cannot allow the rivers of foreign languages to flow out of your belly and do any other thing that requires thought. Speaking in tongues effectively shuts down the minds ability to concentrate. Therefore, time spent speaking in tongues is a fast to the Lord, and controls the soul and flesh of man.
So, Jesus said, "If you believe in me rivers of living water will flow out of your belly and you will do the works I have done, and greater works than these I have done, shall you do." But it takes time to allow rivers of Living Water to flow out of your belly, precious time. Time that you can't spend doing any other thing. This is time devoted to your Lord.
Are you willing to make the sacrifice to allow the rivers of the life of God to flow out of your belly? If you are going to work the works of Christ, you are going to have to believe in His provision for your life, make Him your priority, and allow the rivers to flow.
This will not be easy. Our lives do not allow for much time to be devoted to this purpose. Most of us could carve out fifteen minutes in the shower, or perhaps a couple of minutes on the way to work, but these are not rivers, these are streams or rivulets. We need hours.
This is the reason we can't get the power to witness to work for us. We aren't willing to spend the necessary time allowing the rivers of Living Water to flow through us. Not to mention that the gift of tongues is looked down on by most Church leaders.