Commentary for Kiddushin 122:11

When Abraham instructs his servant to bring a wife for his son, he uses a double formulation: “Thus shall you be freed from my adjuration: if, when you come to my kindred, they refuse you—only then shall you be freed from my adjuration.” This makes sense for R. Meir, but again, why, according to R. Hanina b. Gamaliel is a double formulation needed?
The answer is that if Abraham had only instructed the servant to take a wife for his son (v. 38) we might have thought that if she was willing to go but her family did not want to send her, he should bring her against her family’s will. Hence, Abraham had to stress that she was not to come against her family’s will.