Your words in bold are about demons, and have nothing whatsoever to do with sharing the gospel or the sabbath.
The gospel is the power that cast out lying spirits or demons .Fasting is bringing the gospel or planting the seed. When we sow the seed. We pray and request that Christ cause the growth in a person . . in a hope that it (gospel) will cast out the lies..
Matthew 17:21 Howbeit this kind goeth not out but by prayer and fasting.
Your words in italics are a corruption of Jesus' words from the same story. His actual words are, "This kind only comes out by prayer," not "This kind only comes out by hearing the gospel."
Again fasting is another way of saying bring the gospel planting the seed. The power of gospel cast out the lying spirits as demons.
There is no close connection between the three subjects.
How close are you assuming. Close enough to be used as a metaphor in a parables?
Isaiah 58 is not a parable.
Of course it is. The signified language is clear. That is if a person mixes faith in what they see or hear not avoiding the hidden understanding..
He gives us the 20/20 prescription to fulfill his ministry.
2 Corinthians 4:18 While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.
The spiritually blind see by the power of the gospel. . . the spiritually deaf are given ears to hear the words of His book of prophecy . The power of the gospel gives new spirit life raises those from the dead to new life a new living hope.
Note.... (metaphors in red parenthesis) is the gospel the power of God.
Luke 7:22 Then Jesus answering said unto them, Go your way, and tell John what things ye have seen and heard; how that the blind see, the lame walk, the lepers are cleansed, the deaf hear, the dead are raised, to the poor "the gospel is preached."
John knew he had heard the gospel when he heard it again in Luke. It gave him confidence from our Father to finish his work. . . yoked with Christ.
.Parables uses the things seen the temporal to give the unseen gospel understanding. The Bible is the gospel of Christ. Some try and limit it to four books.
The parable Isaiah 58 as to the spiritual meaning can be compared to the parable spoken of in Luke 7. Remember without parables Christ spoke not. ( Parables are prophecy just as tongues.) All of prophecy is needed to rightly divide the word of God . Can't remove parables or tongues if we are to seek His understanding.
The Isaiah 58 passage is about righteous behaviour, not faith.
Yes it is about those clothed with the righteousness of Christ that works in them to both wil and perform the god pleasure of God.
Can't separate faith the unseen from faith the unseen .
According to Jesus, the sabbath was made for man
I would agree according to the rest (sabbath) it was made for man. Therefor as long as today is today we can enter that rest . We enter that rest by mixing faith (the gospel ) in what we do see or hear.( Hebrew 4)
For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek. For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith. Romans1: 16-17
The justified shall live by His faith not of our selves but the gift of God as labor of His works that we have in these earthen bodies of death.