If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words:
Then shalt thou delight thyself in the Lord; and I will cause thee to ride upon the high places of the earth, and feed thee with the heritage of Jacob thy father: for the mouth of the Lord hath spoken it.
In chapter 57 the Lord tells us that He is with those who are contrite and humble. Only those who know they are broken truly see the character of God in a special way. You cannot fake that and you definitely cannot fool God. Therefore it makes sense that the next thing God does is warn Israel about their insincere worship.
The main point of verses 1-7 is that the people outwardly obey but there is no change in their hearts. They go through all the rituals but it is only lip service. They don’t really mean it. But you cannot truly serve God and become more bitter, self-righteous, and angry. Your character should reflect back on the Lord and cause men to glorify Him.
In verses 8-14 God is telling Israel to stop paying Him lip service and draw near with their hearts. The end of the law is love, as Paul writes, but they do not give their bread to the hungry or open their homes to strangers. They are not acting like the people He wants them to be.
It is easy to forget that following Christ is a process of sanctification. God is daily shaping us into the image of Christ. As we become mature in our faith we should bear the fruit of communion with Him. God is love and when we serve Him we become filled with His love. People should see our kindness and compassion to the brethren, the poor, and the needy.
Our ministry for the Lord should change us and it should change us for the better. The Gardener does not tend to His vineyard without the expectation of bearing fruit. God has a vision for His church and if we are not characterized by the love we have for the brethren then we are not truly serving the Lord.
You need to know what kind of person God wanted to you be and use that to gauge whether you are being obedient to Him.