Considering the cultural context of ancient Israel, what was the primary significance of 'gleaning' (leaving leftover crops for the poor) as exemplified in the story of Ruth?

A It was merely a practical method for efficient harvesting and waste reduction. B It was a symbolic act of rebellion against the established social hierarchy and wealth distribution. C It was a legalistic requirement imposed by the Mosaic Law to ensure strict adherence to religious rules. D It was a divinely ordained system reflecting God's compassion, providing a means for the vulnerable to maintain dignity and sustenance within the community.