Rashi on Genesis 30:21/רש"י על בראשית ל׳:כ״א

1דינה DINAH (Judgment) — Our Rabbis explained, that Leah set herself up as judge (דנה) against herself saying: “If this be a son, my sister Rachel cannot be even the equal of any of the handmaids”. She, therefore, offered prayer regarding it, and its sex was changed (Berakhot 60a).