દોહરો—દૂર્જન તે દૂર્જન હોય, સજ્જન કેમે ન હુવંત;

dōharō—dūrjana tē dūrjana hōya, sajjana kēmē na huvaṁta;

Literally: A wicked person is wicked, a good person cannot become otherwise; neem trees cooked in jaggery do not become sweet.
What it means: An evil person's nature cannot be changed by kindness.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) · 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.