Rashi on Genesis 31:4/רש"י על בראשית ל״א:ד׳

1ויקרא לרחל וללאה AND HE CALLED RACHEL AND LEAH — First Rachel and afterwards Leah for she was the chief wife of the house for whose sake Jacob had entered into relations with Laban. Even the descendants of Leah admitted this (that Rachel was the principal wife), for Boaz and his Law-Court who were of the Tribe of Judah (Leah’s son) said (Ruth 4:11) “like Rachel and like Leah which two did build etc.”, mentioning Rachel before Leah (Genesis Rabbah 71:2).