The couple's Soul2Soul Tour was in Dublin Sunday night, and right after he performed "Humble & Kind" ... Tim reportedly dropped to his knees, then sat down. He left the stage, and Faith came out to say, "He's been super dehydrated. I apologize, but I made the decision that he cannot come back out onstage."
Tim was in the middle of a pretty grueling part of the tour that included 3 cities in 3 days.
He'll have some time to recover -- he and Faith aren't scheduled to perform again until May 31 in Virginia.