Sforno on Genesis 30:31/ספורנו על בראשית ל׳:ל״א

1?מה אתן לך, so that you will achieve what you hope to achieve?

2לא תתן לי מאומה, if the Lord will see fit to bless me, He will certainly not deny you what you are entitled to. Our sages have a rule that a person cannot negatively influence what his fellow human is entitled to. (Yuma 38)