It seems to come ultimately from the account in John 9 where Jesus gives a blind man his sight. Afterwards, the Pharisees conduct a lengthy interrogation of the man, and in verse 25, he replies, "One thing I do know, that though I was blind, now I see," which has roughly the same structure as the line in the Zombies song.
John 9:25 is also one of the sources for the lines "I once was lost but now am found, / Was blind but now I see!" in "Amazing Grace." (The other is Luke 15:24.)
In "In My Mind a Miracle," though, this regaining of sight (probably more metaphorical) is attributed to the charms of a girl, so it's more like Muddy Waters' "She Moves Me," which seems to borrow from the John 9 account (perhaps indirectly via "Amazing Grace") in the lines "She shook her finger at a blind man / 'Once was blind but now I see.'" I don't know if Rod Argent, who wrote "In My Mind a Miracle," was familiar with this particular song, but he was certainly a fan of Muddy Waters. In the Zombie Heaven liner notes (p. 45), Paul Atkinson explains that the Zombies covered "I've Got My Mojo Working" because Rod "wanted to do it" (Johansen notes in Hung up on a Dream [p. 62] that the Zombies even performed "I've Got My Mojo Working" at the Herts Beat Competition).
