In natural zodiac 4th house considered as Karka rashiand also rules heart Jupiter gets exalted in this sign and this dignity is only given to Jupiter only.
In lagna or 10th (4 & 7 also) Jupiter forms powerful Hans yoga while in Kark, Dhanu or Meena rashi. Here Hans stands for two meaning (1) Hans as a bird is supposed to separate milk from water so indicates extreme wisdom (2) Parmatma is also known as Hans and in Hans yoga Jupiter is dignified not Venus.
One of the sign ruled by Venus is Tula and it is an airy sign and other sign of Venus is Vrish an earthy sign and by nature Venus is watery planet so it lacks true spirituality and it does not mean it is not spiritual planet. The water is influenced by the Gravitational force but Guru freed one from the clutches of Gravitational force & Gravitational barrier.
On the other hand Jupiter has Akash Tatwa and one of its sign is Meena a watery sign and its Moola Trikona sign is Dhanur Rashi which is a fiery sign and everyone knows the flames of fire always upwards almost free from the gravity and gravitational barriers.Being of Akash tatwa and filed with these quality this Jupiter or Guru brings one from materialistic approach to spiritual approach and at last to the Parmatma the ultimate approach.
It takes years to understand this in true sense and without the blessing of Guru it is not possible.
(Follow link: https://www.facebook.com/notes/vishal-aksh/who-is-true-guru-deva-guru-brispati-or-asur-guru-shukaracharya/404109593080596 to view this post written by me on my facebook page)