The lyrics of the Lincoln Brewster song “Today is the day” are available here.
This is primarily based on Psalm 118:24:
This is the day that the Lord has made;
let us rejoice and be glad in it.
The song also includes the words “I won’t worry about tomorrow\\ I’m trusting in what you say” which is probably taken from Matthew 6:34:
Therefore do not be anxious about tomorrow, for tomorrow will be anxious for itself. Sufficient for the day is its own trouble.