Answer

In Jain tradition, there is no universally established scriptural rule that says a kadhai must not be used on Dhanteras / Dhanyateras.

This appears to be more of a regional family custom or local belief, not a core Jain religious rule.

Explanation

In many families, Dhanteras is associated with:

• cleanliness and purity,
• auspicious beginning of Diwali days,
• carefulness in food preparation,
• avoidance of unnecessary frying or heavy cooking,
• simple and sattvik food habits.

Because a kadhai is commonly used for deep frying, some families may avoid using it as a symbol of restraint, simplicity, or avoiding heavy/oily food during sacred days.

But this is not a mandatory Jain principle found as a general rule across all Jain communities.

Spiritual Understanding

From a Jain point of view, the deeper focus during Diwali period is:

• remembering Bhagwan Mahavir’s nirvana,
• practicing inner purity,
• reducing attachment and indulgence,
• being careful in food, speech, and conduct,
• doing prayer, pratikraman, charity, and self-reflection.

So if your family avoids using a kadhai on Dhanyateras, it may be followed respectfully as a family tradition, but it should not be treated as a compulsory Jain scriptural rule.

Takeaway

There is no specific Jain scriptural reason generally known for not using a kadhai on Dhanyateras. It is most likely a family or regional custom, possibly connected with simplicity, purity, and avoiding fried food during auspicious days.