According the classical astrological work, Phaladeepika by Sage Manthreshwara, the 9th House in an individual’s Natal Chart holds the key to unlock one’s past birth.
In fact, most Indian astrologers use the term, Purvapunyasthana to describe the 9th House in a horoscope.
If the 9th lord is debilitated or in an enemy’s House, one’s previous birth was in a different country. If the 9th lord is exalted, the native in previous birth was brought up and lived in a high society of good people.
If the 9th lord is in his own House or in a friend’s House, the past life was in the same country as the native has been born in this lifetime.
If the 9th lord is Jupiter, the native was born and brought up in Aryavarta, in the region between the Himalayas and the Vindya mountains.
If the 9th lord is Venus or the Moon, the native was born in his previous lifetime near a Punyanadi (a good river) such as Kaveri.
If the 9th lord happens to be Mercury, the past birth happened near the Skshetras of Gods like Vishnu and Shiva (a reference to Shrirangam and Chitambaram in India)
If the 9th lord is Saturn, the person was born in a Mlechcha Desha outside Bharat Varsha. (in a land of barbarians or uncivilized people outside the part of ancient India
(Bharat Desh) called Bharat Varsha.
If the lord of the 9th House is Sun, the birth took place in a forest or a mountainous region.
If the lord of the 9th House is Mars, the person was born in a place where life is difficult.
The method to determine the kind of life in the past birth:
as expounded in Phaladeepika is as follows:
If the 9th lord is placed in a Prushyodaya Rashi (sign rising from the hind part) – a movable sign - the native was some plant in the previous birth.
If the 9th lord is placed in a Shirshayodaya Rashi (sign rising from the head) – the person was a living being like an animal or a human being.
If the 9th lord is placed in the sign of exaltation, or own sign or in a friend’s sign of the Lagna lord, the previous birth was that of a human being.
If the 9th lord is placed in a neutral sign of the Lagna lord, the previous birth was that of an animal.
If the 9th lord is placed in an enemy sign of the Lagna lord, the previous life was that of a bird.