In Vedic astrology Seventh house is mainly the house of spouse. It has various names in Sanskrit  called as Jamitra, Asta, Dyun, Mrityu etc. It signifies Chittottha ( उत्तेजना), Mada (Sexual passion or Proudness or घमंड),  Kama (desire or sexuality ), Adhvan (way or road), Loka (people), Pati or dara (husband), Marga (way  i.e. short journey) and Bharya (wife) are belong to 7th house. What would be the result according to Parashar  when 7th lord occupied duhsthan that is trik houses 6-8-12 in birth chart? It is explained in these three verses-

दारेशे व्ययगे जातो दरिद्रः कृपणोअपि वा।
भार्याअपि व्ययशीलाअ्स्य वस्त्राजीवी नरो भवेत्।।

when 7th house lord placed in 12th house than native may be poor and miserly in expense but his wife may be expensive by nature. Native’s livelihood will be related to clothes. Native may be poor.

दारेशे मृत्युभावस्थे जातो दारासुखज्क्षितः।
भार्या अ्पि रोगयुक्ताअ्स्य दुःशीलाअ्पि न घानुगा ।।

When 7th house lord in 8th house then native will be devoid from happiness of wife. His wife may be either sick and will have disease or characterless or not under control of native.

दारेशे रिपुभावस्थे भार्या तस्य रूजान्विता।
स्त्रिया सहाअ्थ वा वैरं स्वयं क्रोधी सुखोज्जितः।।
When 7th house lord placed to 6th house than his wife will be sick. If not sick then he will have enmity with his wife. He may be angry by nature and without any happiness.