Why did Yakov ask Lavan for his wives and children before taking leave from him?
Rashi: This was Yakov's way of asking Lavan for permission to leave. 1 (He felt that this was the correct thing to do - EC.)
Seforno: Lavan, who was an important dignitary in Charan, would let him depart on the long journey home only if he could supply his family with their basic needs. If not, Lavan's daughters and grandchildren would be in danger. Even though Yakov did not yet own sheep or cattle, he could supply their basic needs.
רש"י: תנה את נשי וגו' - איני רוצה לצאת כי אם ברשות: מנין לרש"י לפרש כך?
גור אריה: מלשון "תנה" משמע שביקש רשות שהרי לבן לא החזיק בהם.