The oṁkāra, praṇava, is the Supreme Personality of Godhead represented by letters. Bhagavad-gītā says that the letters a-u-m, combined together as om, represent the Supreme Lord. Religious principles are meant to invoke the blessings and mercy of the Supreme Personality of Godhead, Kṛṣṇa, who says in Bhagavad-gītā that He is personally present in sexual desires that are not contrary to religious principles. The word vidhinā means, “according to religious principles.” The association of men and women according to religious principles is allowed in the Vedic culture. In our Kṛṣṇa consciousness movement we allow marriage on the basis of religious principles, but the sexual combination of men and women as friends is irreligious and is not allowed.