On May 3, 1950 — 1950 – New York Yankees pitcher Vic Raschi, troubled by the new rule that requires a one-second stop before delivery with men on base, balks four times in one game, a club record and two fewer than the single-season record. Nevertheless, Raschi wins, 4 – 3, over the Chicago White Sox. He will finish the season with six balks to tie the since-topped American League mark.

Source:
Baseball Reference May 3