#So they sent their sister Rebekah

"So the family sent Rebekah"

#their sister

Rebekah was Laban's sister. AT: "their relative" or "Laban's sister"

#her female servant

This refers to the female servant who had fed Rebekah when she was a baby, cared for her when she was a child, and still served her.

#Our sister

Rebekah was not the sister to everyone in her family. But they called her this to show that they loved her. AT: "Our dear Rebekah"

#may you be the mother of thousands of ten thousands

Here "mother" stands for ancestor. AT: "may you be the ancestor of millions of people" or "may you have very many descendants"

#thousands of ten thousands

This means a very large number or an uncountable number. (See: [[:en:ta:vol2:translate:translate_numbers]])

#may your descendants possess the gate of those who hate them

Armies would break through the gate of their enemies' cities and conquer the people. AT: "may your descendants completely defeat those who hate them" (See: [[:en:ta:vol2:translate:figs_metonymy]])