Or HaChaim on Numbers 24:2/אור החיים על במדבר כ״ד:ב׳

1 וישא בלעם את עיניו, Bileam raised his eyes, etc." The Torah had to write Bileam's name once more as well as the word וישא, "he raised." Seeing that we have explained earlier that the Israelites were surrounded and enveloped by G'd's protective cloud so that no evil eye could harm them, the Torah had to tell us that Bileam "raised" his eyes, i.e. that he invoked the prophetic powers with which he had been equipped, in order to see what ordinary people could not see (compare verse 4: "who sees the vision of G'd…with open eyes"). The Torah describes things Bileam saw with his mental eye. His name was mentioned here once more in order to make clear that what Bileam did here he did in his capacity as a prophet designated by G'd to the Gentile nations. He succeeded in seeing the Israelites as a result of invoking these powers G'd had equipped him with.

2וירא את ישראל שכן לשבטיו, "He observed the Israelites encamped according to their tribes. He was overcome by the Holy Spirit." Bileam discovered two things of importance. 1) The Israelites were disciplined, each tribe occupying the area assigned to it, their leader at their head. The reason for this separation of the tribes was that each tribe represented a spiritual level all its own. 2) The Holy Spirit rested on the people. It is also possible that Bileam realised the truth of the statement in Baba Batra 60 that the reason the people qualified to have the Holy Spirit rest on them and to have become the מרכבה, G'd's chariot, as it were, was that each tribe had arranged to be a closed unit.