This kind goes not out
Yes, that blessings are to be obtained in the use of this means which are otherwise unattainable, our Lord expressly declares in his answer to his disciples asking: Why could we not cast him out? Jesus said to them: Because of your unbelief. For truly I say to you, if you have faith as a grain of mustard seed, you shall say to this mountain, remove from here to yonder place, and it shall remove, and nothing shall be impossible to you. However, this kind (of devils) does not go out but by prayer and fasting (Matthew 17:19-21). These being the appointed means of attaining that faith whereby the very devils are subject to you.
1771 text
Yea, that blessings are to be obtained in the use of this means, which are no otherwise attainable, our Lord expresly declares in his answer to his disciples asking, Why could not we cast him out? Jesus said unto them, Because of your unbelief; for verily I say unto you, if ye have faith as a grain of mustard-seed, ye shall say unto this mountain, remove hence to yonder place, and it shall remove, and nothing shall be impossible unto you. Howbeit, this kind (of devils) goeth not out, but by prayer and fasting: these being the appointed means of attaining that faith, whereby the very devils are subject unto you.