Once a disciple went to a preceptor and requested him to impart to him the Supreme knowledge of the Omniself (Brahma Thathwam). The Guru gave him a mantra and asked him to chant it continually without any selfish desire. The Guru told him that after he had done this sadhana for one whole year he could come to receive the knowledge of the Supreme (Brahma Jnana).

The disciple approached his Guru after one year and told him "Oh revered one! I have recited the mantra for one whole year". He was eagerly awaiting the preceptor's answer. He thought that his Guru would certainly impart to him the knowledge of the Supreme. Just then, unaware of the presence of the disciple, the maid servant was sweeping the ashram premises and the dust from the ground fell on the young man. The disciple flew into a rage, because he had come to the ashram after a sacred bath and the dust had sullied his body. He looked at her with anger and the maid was filled with fear. The Preceptor was watching the entire scene.

The Guru said "you are not competent to receive the knowledge. You got angry with the maid servant who unwittingly caused some dust to fall on you. How can Brahma Jnana be imparted to one, who has not that much of endurance? Go back and practice the Sadhana for one more year".

At the end of the second year the disciple was about to enter the ashram. According to the instructions of the Guru the maid servant once again let the dust fall on the disciple in full measure. The disciple grew indignant and wanted to beat her, but somehow, refrained from doing so.

The disciple approached the Guru and paid his respect. The Guru told him: "You are still not competent to receive the knowledge. Last year you exhibited the qualities of a snake and now those of a dog. Come back after ridding yourself of these animal qualities".

At the end of the third year, the disciple entered the ashram premises after taking a sacred bath. As per the instructions of the Guru the maid servant poured some dirty water on the disciple. The disciple calmly offered his salutations to the maid and said, "Mother! I offer my salutation to you. You have helped me to acquire the greatest virtue, forbearance. Now I am worthy enough to receive the grace of my Guru. I shall always be grateful to you".

As soon as the disciple prostrated before the Guru, the Guru endearingly said: "Son! Now you are quite competent to receive the knowledge of the Supreme".

Source: Chinna Katha II, 215