Stephen Schwartz’s credit for Godspell is  “music and new lyrics.” On this list of lyric sources, you’ll see which song lyrics were adapted or drawn from hymns, and which were original to Schwartz.
“Prologue”: various philosophical sources adapted by Tebelek, revised by Schwartz Summer 2000.
“Prepare Ye”: Matthew 3:3 (Isaiah 40:3)
“Save the People”: Episcopal Hymnal 1940, no. 496
“Day by Day”: E. Hymnal, no. 429 (from Richard of Chichester)
“Learn Your Lessons Well”: Original lyric by Stephen Schwartz
“Bless the Lord”: E. Hymnal, no. 293 (adaptation from Psalm 103)
“All for the Best”: Original lyric by Stephen Schwartz
“All Good Gifts”: E.Hymnal no. 138
“Light of the World”: Adaptation of Matthew 5:13-16
“Turn Back, O Man”: E. Hymnal no. 536
“Alas for You”: Inspired by Matthew 23:13-37 (Adapted by Stephen Schwartz)
“By my Side”: Original lyric by Jay Hamburger
“We Beseech Thee”: E. Hymnal no. 229
“On the Willows”: Adaptation of Psalm 137
“Finale”: Lyric by Stephen Schwartz; reprise of Matthew 3:3
“Beautiful City”: Stephen Schwartz wrote the music and lyrics for the film version of Godspell. They were revised for a production of Godspell to be done in Los Angeles to benefit the Inner City after the Rodney King riots.
SOURCE: Data from The Godspell Experience, The Broadway Musical in the chapter “Religious Experience as Musical” and the forum.
Note that the lyrics in the hymnal were from earlier sources.