What is the difference between sustenance (rizq) and commercial profit, and is sustenance limited to what a person eats and wears, or does it include what he earns from work and trade?

Sustenance (rizq) is broader than commercial profit; every profit is sustenance, but not all sustenance is profit. Sustenance is everything that Allah bestows upon His servant, both in worldly and religious matters. It is what benefits a person, and it encompasses visible sustenance for the bodies, such as provisions, and inner sustenance for the hearts, such as knowledge and insights.