The first Sabbath of each month is reserved for prayer and fasting.

Matthew 17:20-21

So Jesus said to them, “Because of your unbelief; for assuredly, I say to you, if you have faith as a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you. ²¹ However, this kind does not go out except by prayer and fasting.”