You should assure him with references to the past whose sense you want to control. A wicked man should be assured by promises of future well-being.
यस्य बुद्धिः परिभवेत् तमतीतेन सान्त्वयेत्। अनागतेन दुष्प्रज्ञं प्रत्युत्पन्नेन पण्डितम्॥