John Calvin Commentary Matthew 8:13

"And Jesus said unto the centurion, Go thy way; as thou hast believed, [so] be it done unto thee. And the servant was healed in that hour." — Matthew 8:13 (ASV)

Go away, and as thou believest, so may it be to thee. Therefore, it is evident how graciously Christ pours out his grace when he finds the vessel of faith open. Though he addresses these words to the centurion, there can be no doubt that, in his person, he invites us all to strong hope. Thus, we are also taught the reason why God is, for the most part, so limited in his communications to us: it is because our unbelief does not permit him to be liberal. If we open up the entrance to him by faith, he will listen to our wishes and prayers.