Jordan Spieth cost him and Patrick Reed the 12th hole in their Saturday afternoon fourball match against Jason Day and Louis Oosthuizen at the 2017 Presidents Cup -- and it was all because of a courtesy Spieth paid Day.
— PGA TOUR (@PGATOUR) September 30, 2017
Oosthuizen's putt on the drivable par 4 had missed and was rolling well past the hole. So, rather than making the Aussie chase it, Spieth stopped it with his putter and handed it back to him. Why not, Day was already in with birdie for the Internationals. However, Spieth stopped that ball on purpose while he was still relevant to the hole, as he had a putt for birdie. That meant Spieth violated Rule 1-2 of the Rules of Golf by stopping the ball without expressly being asked by the opponent. In team match play, the penalty for breaking that rule is the disqualification of the offending player for that hole.
The end result was the Internationals won the 12th to take a 1-up lead in the match.
Day and Oosthuizen talked to the rules official with the match, saying they didn't want to win that way and that Day's rolling ball became irrelevant when the stroke missed the hole. However, Rule 1-3 says players cannot mutually agree to waive any rule or penalty, so the ruling stood, even as Tiger Woods and the other players asked the referee for a better explanation or to change the ruling.