Or HaChaim on Genesis 29:10/אור החיים על בראשית כ״ט:י׳

1 ויהי כאשר ראה יעקב את רחל, It was when Jacob saw Rachel, etc. The reason that the Torah repeats three times that Laban was the brother of Jacob's mother is to emphasise that everything Jacob did was only because Laban was his mother's brother and he tried to honour his mother by carrying out her instructions. Another reason for the Torah to repeat this information was so that bystanders who observed Jacob- a recently arrived total stranger- doing Rachel such a great favour (removal of the stone on the well) would know that he was motivated only by family considerations. This is why Jacob spelled out his reasons and as soon as he laid eyes on Rachel he mentioned that she was the daughter of Laban who was his mother's brother. This is also why he displayed concern about the flocks of his uncle. When he kissed Rachel he did not repeat this statement since he had already made plain that Rachel was his cousin. Besides, the very fact that he started crying was explanation enough that he had come face to face with a relative.

2When the Torah repeats that "Jacob watered the flocks of Laban," the message may be that he did this only because Laban was his mother's brother. Otherwise, -in line with what we learn in Avodah Zarah 67- there was no call to do favours to the Gentiles, seeing that we know from Proverbs 14,34: "(even) the kindness done for us by the Gentile nations are a form of sin."