Answer

Before doing Navkarsi, the common Pachchakkhan is:

“Uggai suriye, Navkarsi pachchakkhāmi.”

Meaning: “I take the vow to not eat or drink until Navkarsi time after sunrise.”

Important

Please take Pachchakkhan from a Sadhu-Sadhvi Bhagwant or a knowledgeable Jain person if possible, because pronunciation and tradition may differ slightly by sampraday.

Takeaway

For Navkarsi, say Navkarsi Pachchakkhan before sunrise/at the proper time, with devotion and awareness.