આગે આગ મળે, ત્યારે ભડકા થાય.

āgē āga maḷē, tyārē bhaḍakā thāya.

Literally: When fire meets fire, then there are flames.
What it means: When two volatile or strong-willed people clash, the conflict intensifies.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) 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.