Koyle ki dalali mein mooh kaala, gar saath aibi bando ka rakhe Rahu baara wala.
In the brokerage of coal, the face gets blackened; if the one with Rahu in the 12th keeps the company of flawed/addicted people.
Dr. Sharma uses a famous Hindi proverb to explain the greatest vulnerability of a person with Rahu in the 12th house.
The 12th house rules hidden activities, addictions, and losses. Rahu is the planet of illusion and bad habits. When Rahu sits here, the native is highly susceptible to the energy of the people around them.
If they associate with people who have bad habits, addictions, or criminal tendencies ("aibi bando ka saath"), they will inevitably be dragged down with them. Just as dealing in coal guarantees your hands and face will get dirty ("koyle ki dalali mein mooh kaala"), hanging around toxic people will guarantee the destruction of Rahu 12's reputation and life.