1 of 5 | Pitcher Landen Roupp was among the San Francisco Giants players who wrote Bible references on their hats earlier this month on Pride Night in San Francisco. File Photo by Tannen Maury/UPI | License Photo

June 23 (UPI) -- A communication "lapse" by the San Francisco Giants led to players writing Bible verses on their Pride Night hats, MLB commissioner Rob Manfred said.

Manfred spoke about the issue through a letter sent Friday to Sen. Josh Hawley, R-Mo. Hawley posted the letter Monday night on social media. The Giants did not immediately respond to a request for comment.

MLB issued warnings to several Giants players last week, pointing to uniform-related rules violations committed during their 5-1 loss to the Chicago Cubs on June 12 in San Francisco.

Giants pitchers Landen Roupp, J.T. Brubaker and Ryan Walker had placed Biblical references on their hats. Fellow pitcher Sam Hentges wore a plain black Giants cap instead of a Pride Night one.