Source: BG 3.35 Purport
Everyone has to cleanse his heart by a gradual process, not abruptly. However, when one transcends the modes of material nature and is fully situated in Kṛṣṇa consciousness, he can perform anything and everything under the direction of a bona fide spiritual master. In that complete stage of Kṛṣṇa consciousness, the kṣatriya may act as a brāhmaṇa, or a brāhmaṇa may act as a kṣatriya. In the transcendental stage, the distinctions of the material world do not apply. For example, Viśvāmitra was originally a kṣatriya, but later on he acted as a brāhmaṇa, whereas Paraśurāma was a brāhmaṇa but later on he acted as a kṣatriya. Being transcendentally situated, they could do so; but as long as one is on the material platform, he must perform his duties according to the modes of material nature. At the same time, he must have a full sense of Kṛṣṇa consciousness.