Philo of Alexandria was a Hellenistic Jewish philosopher who lived in Alexandria in the Roman province of Egypt during the First Century. The following paraphrase of this passage in the Book of Genesis comes from his Life of Moses, which reflects his understanding of the oral Jewish interpretation of this passage during the First Century.
Life of Moses § 50
“Balak has sent for me from Mesopotamia, having caused me to take a long journey from the east, that he might chastise the Hebrews by means of curses. But in what manner shall I be able to curse those who have not been cursed by God? For I shall behold them with my eyes from the loftiest mountains, and I shall see them with my mind; and I shall never be able to injure the people which shall dwell alone, not being numbered among the other nations, not in accordance with the inheritance of any particular places, or any apportionment of lands, but by reason of the peculiar nature of their remarkable customs, as they will never mingle with any other nation so as to depart from their national and ancestral ways. Who has ever discovered with accuracy the first origin of the birth of these people? Their bodies, indeed, may have been fashioned according to human means of propagation; but their souls have been brought forth by divine agency, wherefore they are nearly related to God. May my soul die as to the death of the body, that it may be remembered among the souls of the righteous, such as the souls of these men are.” (Emphasis added)
SOURCE: Yonge, C. D. with Philo of Alexandria (1855). The Works of Philo: Complete and Unabridged. London: Henry G. Bohn, 61.