Mahas is the sun. All the worlds are increased by the sun. Bhu is Agni (fire), Bhuvas is Vayu (air), Suvas is Aditya (sun). Mahas is the moon. All the heavenly lights are increased by the moon. Bhu is the Rik-verses, Bhuvas is the Saman-verses, Suvas is the Yagus-verses.

In plain words: The fourth word, Mahas, is linked to the sun, because the sun makes all the worlds grow. In another set, Bhu is fire, Bhuvas is air and Suvas is the sun, while Mahas is the moon, which makes all the lights in the sky shine brighter. In a third set, the three words stand for the three kinds of Vedic verses: Rik, Saman and Yajus.