Opinions of ancient expert saint-astrologers :-
Now I describe the effect of Guru (Jupiter) in the sixth bhaava. Lagnath shashtame Guru-phalam. Sixth house denotes enemies, cousins (jnaathis), sickness, diseases, nursing, food, service, employees, subordinates or servants, debts, cattle, tenants, enemies, maternal uncle, miserliness, intense anguish, litigation etc.
Effects : Views of renowned astrologers : 1) Saint-Astrologer Maharshi Parasara (Great grand-father of Pandavas and Kauravas of Mahabharatha epic; father of Maharshi Veda Vyasa) wrote : (sloka = Sanskrit verse) :-
SANGEETHA-NAATYA-HATHA CHITTHA-VRUTHI, KEERTHI-PRIYO, ARI-JANA PRAHARTHA, PRARBDA-KARYA LASKRUTH NARASYAATH, DEVA-GURU YADI SATHRU-SAMSTHAE = IF GURU (JUPITER) IS IN 6TH HOUSE, THE PERSON ( HE / SHE) HATES MUSIC, DANCE & FINE ARTS; YEARNS FOR NAME & FAME; VANQUISHES / DESTROYS ENEMIES; HAS FIRM FAITH IN SUPERSTITIONS. HE / SHE IS FREE FROM DISEASES; STURDY, HALE & HEALTHY.
2) Bhrigu Sutras- by saint-astrologer Maharishi Bhrigu (3500 BC):-- Suthra (32) :-
Explanation :- According to above Sutras Jupiter as a natural benefic will give good effects in regard to the significations of the sixth house unless he is afflicted. This sixth house is not a significator of children or grand children. It is, therefore, not understood how the effect will be realised if Jupiter is in the sixth house. The sixth house is an evil house (dusthana) and if Jupiter is there as a lord of an auspicious house, the significations of that house will be adversely affected.
3)Brihath Jataka by Varhamihira (325 AC) :- The person concerned will be without enemies.