كَثِيرُ الرَّمَادِ إِذَا مَا شَتَا
Abundant in ash in winter; the intended meaning is lavish hospitality and generosity.
Frequent guests lead to much cooking; much cooking demands more fire; more fire produces more ash. The inference proceeds through ash → fire → cooking → hospitality → generosity.
Mentioning winter strengthens the setting of warming fires and hospitality. The point is not ash itself but an indirect, memorable presentation of generosity.