In between the Apostle Paul’s first and second letter to the Thessalonians we read three Psalms and one chapter of Isaiah.
Psalm 95 is a song of praise to God, but also a warning that they should not harden their hearts as they did in the wilderness and thus were not allowed to enter God’s rest.
Psalm 96 is to “declare His glory among the nations“, and ends up with “Let all creation rejoice before the Lord, for he comes, he comes to judge the earth.”
Psalm 97 tells what it means to rejoice “for the LORD reigneth” and “For you, Lord, are the Most High over all the earth; you are exalted far above all gods.”
Isaiah 58 explains what true fasting is.