The 9th house is the house of Dharma, tradition, and elders. Rahu is the planet of rebellion, foreign things, and breaking boundaries.
When Rahu sits in the 9th house, the person naturally rebels against their own culture. Dr. Sharma gives two strict behavioral warnings for this placement.
First, never cross the line of disrespect ("badtameezi"), especially toward elders or religious figures. Second, do not become obsessed with foreign languages, foreign cultures, or foreign slang ("videshi boli se pyaar"). Abandoning your native tongue and traditions to adopt a foreign identity will activate the negative, destructive side of Rahu in the house of destiny.