So, lets see what Jupiter can do in 3rd house without any conjunction or aspect from any other planet. 1st lets see what these 2 things represent --
Jupiter is the most benefic planet and it represents all the auspicious things like Knowledge, Wisdom, Law, Guru, Spirituality, Religion, Philosophy, Literature, Elderly People. For a girl, Jupiter also represents Husband.
3rd house - It is house of your communication skills, neighbours, short distance travels, younger siblings, marketing, announcements, collecting information, hobbies and skills, self-efforts, business, courage etc.
3rd house is house of communication and Jupiter is planet of Wisdom, so 1st of all this person's communications would be filled with wisdom. It is not necessary that they will be preachers or saints but whatever they say, will have some good message involved within it. They can be seen as Preachy in Society. Jupiter here makes a person a very good businessman but in his 30s as it is one of Upachaya Houses, which grows with time. They also become very good writers and truthful journalists. They can be like a Guide to their siblings.
From 3rd house, Jupiter aspects the 7th house of marriage. It shows the need to educate yourself in matters of relations and business.
Jupiter's next aspect goes to 9th house of religion, philosophy, pilgrimage and almost all the things which Jupiter represents. So, Jupiter's aspect further expands the quality of 9th house gradually and makes a person highly religious and philosophical.
Jupiter's last aspects goes to 11th house of gains, network circles, elder siblings. So, these people gain from their siblings, either elder or younger. They have large network circles and friends. They can be very good with money matters. But all these results in 30s as 11th house is again Upachaya Houses. So, before 30, person needs to learn about how to deal with all these matters.
Next - Jupiter in 4th house.
Vishal S Saxena - Astrologer