પીતળ માણસથી કામ પાડતાં સચેત રહેવું.

pītaḷa māṇasathī kāma pāḍatāṁ sacēta rahēvuṁ.

Literally: Be alert when dealing with a brass person.
What it means: Exercise caution when interacting with deceitful or hypocritical individuals.

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.