Chasidut zu Bereschit 26:28

Genesis 26,28. “we have taken due note of the fact ‎that the Lord has been with you, etc.;” based on what we ‎explained (18,2) in connection with ‎וירא וירץ לקראתם‎, (page 88) ‎that when a person looks at a righteous person, his own powers ‎of perception are enhanced by the mere fact that he is within the ‎orbit of the tzaddik, our sages (Rosh Hashanah 16) have ‎stated that people must make a point of visiting their Rabbi or ‎other scholars on the festivals. They will benefit spiritually merely ‎by looking at their Rabbi. Avraham at the time had realized that ‎the three strangers who had appeared in front of him suddenly ‎were superior beings as his own powers of perception had been ‎sharpened by their arrival and his facing them. It was this ‎realization that his perceptive powers had been enhanced, that ‎prompted him at the time not only to walk toward these visitors ‎but to run in order to make them welcome.‎
The repetition by the Torah of the words ‎ראו ראינו‎ is to draw ‎our attention to both Avimelech and his entourage having ‎experienced these enhanced powers of perception. They had ‎become aware that their powers of “seeing” had not only been ‎improved quantitatively but also qualitatively, i.e. they had ‎experienced the awe of feeling in the presence of a spiritually ‎superior being. They realized now that the Presence of the Divine ‎Shechinah rested above the head of Yitzchok.‎