Parsha Chayei Sarah - Chapter 24 - Verses 58-60
Laban (Rivka's brother) seemingly blesses Rivka by saying you should become this great nation and may your offspring inherit the gates of your enemies. Meaning, your offspring should be very successful, they should be on the upper hand, rather than the lower side.
However, these famous words said by Laban were not a blessing. Rashi says Laban was trying give Rivka a curse. When a person checks out a girl for marriage, you are supposed to check out the brothers of the girl. Often times, the children will turn out like her brothers. So in essence, he was actually cursing her. He is saying, so should you children be wicked like me!