On July 7, 1979 Mike Schmidt homers in his first three times up for the Phillies, to give him a major league record-tying four straight over two games. Schmidt flies to the warning track in his next at bat, and the Phils lose, 8 – 6 to the Giants. Schmidt will hit three more home runs in the next three games to tie the National League record of seven home runs in five games.

Source:
Baseball Reference July 7