זוהר בראשית — דף קכז ע”ב

The Zohar explains that Abraham acted with propriety: he first asked for something others did not need, and when the sons of Heth said to him “you are a prince of God among us,” he asked to meet Ephron son of Zohar, saying he wished to be buried among them so as not to be separated from them. Rabbi Elazar explains that Abraham entered the cave while running after the calf that had fled there; he adds that Abraham prayed every day in that field, saw the light coming out of the cave, and that the Holy One, blessed be He, spoke with him there. He did not ask for it earlier so that no one would notice; when the need arose, he said the time had come. Finally, had Ephron seen in the cave what Abraham saw, he would never have sold it; the matter is revealed only to its owner, and Ephron saw nothing but darkness.