Sforno on Deuteronomy 16:12/ספורנו על דברים ט״ז:י״ב

1וזכרת כי עבד היית, where you did not own any money of your own, seeing that whatever is in the hands of a slave is owned by his master. (Pessachim 88)

2ושמרת ועשית את החקים האלה, by leaving behind gleanings, the peyah, etc., as a goodwill gesture for your G’d Who has taken you out from there and given you wealth and landed property.