દાઢ હાથીના પેટમાં પણ બોલે.

dāḍha hāthīnā pēṭamāṁ paṇa bōlē.

Literally: The molar tooth speaks even inside an elephant's belly.
What it means: A deeply hidden truth or secret desire eventually finds a way to reveal itself.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1921) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.