ולכהן, הרועים עשו התקשרות ביניהם כמו שעשו רועי חרן שלא ישקו הצאן עד אשר אם יתאספו כל העדרים כי היו המים ביוקר ומצד זה הקפידו על בנות מדין שהקדימו לדלות ולהשקות לפני הרועים, אמנם משה ראה שהדין עמהם מפני ארבעה טעמים, א] שההתקשרות שעשו הרועים ביניהם אינו חל על יתרו שהיה כהן מדין שמצד כהונתו נוטל חלק בראש וי״ל משפט הקדימה, ב] שהיו שבע בנות ומצד שהם נקבות אין ראוי שימתינו על הרועים מפר הצניעות, ג] מצד עצם הענין שכבר באו ודלו ותמלאנה את הרהטים והיו המים שלהם, ד] שההתקשרות אינו חל רק על רועים שרועים צאן של אחרים, אבל הם באו להשקות צאן אביהן ואינם בכלל הרועים, ובכ״ז: [מלבי"ם]
THE PRIEST OF MIDIAN HAD SEVEN DAUGHTERS.
[Why did he intervene, considering that the shepherds had so agreed among themselves?]
Water was scarce and therefore the shepherds agreed among themselves not to water their sheep until all the flocks will have been gathered — just as the shepherds of Haran had once done.Accordingly they set upon the daughters of the priest of Midian for having drawn water before the other shepherds had arrived.
Moshe, however, considered them to be in the right — on four counts. (1) The arrangement which the shepherds had among themselves did not apply to Yithro as the priest of Midian: the right of precedence was part of the priestly privilege, and he was thus entitled to receive his portion ahead of others. Moreover, (2) he had seven daughters, and female modesty dictated that it was not becoming to have them wait for the shepherds. (3) As they had already filled the troughs, the water belonged to them. (4) The agreement to wait for everyone to assemble applied only to shepherds who pasture the sheep of others, whereas they came to water their father's flock, and thus were not to be regarded as shepherds.
Lessons:
1] Even Midianite girls have to be modest.
2] An agreement is an agreement but one must have his eyes open to see where it doesn't apply.