Jupiter. The perfect Guru
http://www.vedicwisdom.com/jupiter.php
Jupiter is the most benific planet in Vedic Astrology. That is the reason he is called Guru in Hindi. Guru means Guide . Even if a guru is harsh on his disciples he is being harsh out of compassion. Mercury is named Budh, now budh can be a Buddha if favorable or a Buddhu if detrimental. But Guru is Guru!
http://www.vedicwisdom.com/jupiter.php