Walker tweeted Sunday, "Philipians 4:13."
Philippians 4:13— Governor Walker (@GovWalker) March 16, 2014
That verse reads, "I can do all things through Christ who strengthens me."
The atheist group FFRF wants Walker to delete the tweet, citing the separation of church and state.
The group sent a letter to Walker on Tuesday telling him it's "improper for a state employee, much less for the chief executive officer of the state, to use the machinery of the state of Wisconsin to promote personal religious views."
As of Friday morning, the tweet was still on Walker's Twitter page.