And Jesus said to him, " 'If You can?' All things are possible to him who believes."
And He said to them, "This kind cannot come out by anything but prayer." (Mark 9:23, 29 NASB)
(We missed an important point and are returning to verse 44 to glean it.)
The word translated as "sink" is one that conveys the idea of laying up or storing. Another way of saying this might be "let My works soak into and through you". Jesus' intent was for the disciples to do more than let His words go in one ear and out the other. He intended for His words to "sink in" and stay there.
Which words did Jesus want us to store? All of them. Every word He spoke was given to us with His face looking toward the cross and His eyes focused on eternity. His words were given that we might be prepared for what is to come. This story is also related in Mark's gospel, which included a few more details. I have pulled out a few of those words of Jesus from the Mark passage. First, "all things are possible to him who believes." What does "all" include? Any manner of healing is possible. Some healing will only be accomplished in heaven, but much healing could be accomplished here on earth, if we had the faith to request it. Jesus did not put a limit on the things for which we ask, only that we should ask in the name of Jesus and for the perfect will of the Father.
Some things "can only come out (or be healed) by prayer (or by prayer and fasting)". This is still true. Perhaps the reason we do not see miracles in our American churches today is that we are not willing to deny ourselves by fasting and praying with intensity. I am not saying that, if your prayer was not answered in the way you wanted, it was because you didn't pray hard enough or long enough. In the end, it is God's will that must be done. Our job is to humble ourselves, repent of our sins, fast and pray.
This is a hard word for the American church, and it grieves me to say it, but we need to hear it. Let these words sink in and hold to them. Our inability to see the miraculous signs and wonders of God in this country does not mean that God is unable to do miraculous signs or wonders, nor does it mean that they are not happening. According to numerous reports from first-hand observers, the blind are regaining their sight. The deaf are regaining their hearing. The dead are being raised. These miracles are not happening as a result of medical intervention. They are happening in places where there is no medical intervention. You may have heard the saying, "When God is all you have, you learn that He is all you need." It turns out that those words are true, and people in the most remote places on earth can attest to it. They still see God move. Miracles still happen.
Our job is to know the heart of God and not just the hand of God. When we intimately know the heart of God (faith) by allowing His words to sink in like a gentle summer rain, we, too, may begin to see our prayers answered in ways too marvelous for us to imagine. It all begins with this one thing. Let His words sink in and take root. The fruit they can bear is more marvelous we can imagine.