PURPORT

Vasudeva and Nanda Maharaja were so intimately connected that they lived like brothers. Furthermore, it is learned from the notes of Sripada Madhvacarya that Vasudeva and Nanda Maharaja were stepbrothers. Vasudeva's father, Surasena, married a vaisya girl, and from her Nanda Maharaja was born. Later, Nanda Maharaja himself married a vaisya girl, Yasoda. Therefore his family is celebrated as a vaisya family, and Krsna, identifying Himself as their son, took charge of vaisya activities (krsi-go-raksya-vanijyam). Balarama represents plowing the land for agriculture and therefore always carries in His hand a plow, whereas Krsna tends cows and therefore carries a flute in His hand. Thus the two brothers represent krsi-raksya and go-raksya.