וְעַתָּ֥ה בְנִ֖י שְׁמַ֣ע בְּקֹלִ֑י לַאֲשֶׁ֥ר אֲנִ֖י מְצַוָּ֥ה אֹתָֽךְ׃
Now therefore, my son, hearken to my voice according to that which I command thee.
Or HaChaim on Genesis
ועתה בני שמע בקולי, "and now my son, listen to me and obey my instructions!" "hasten to bring me two young kids at once."
Haamek Davar on Genesis
Listen to my voice as I instruct you. The word “to my voice” is redundant. What would have been lost had the scripture merely said “Listen as I instruct you”? We have already explained that every place “my voice” is used careful attention and understanding is implied. She told him to listen carefully as she was commanding, to hint to him that she is speaking with Divine authority.