Which Vedic text contains 1,028 hymns organized into 10 books called mandalas and is considered the most substantial and significant of the collection?

The Rig Veda is the oldest and most extensive of the four Vedas, comprising 1,028 hymns (including the Valakhilia hymns) organized into ten books known as mandalas. These hymns were composed in Vedic Sanskrit, an archaic language that gradually evolved into classical Sanskrit. The Rig Veda holds particular significance as it forms the foundation of Hindu philosophical thought and contains many of the oldest known Indo-European religious texts. The four Vedas—Rigveda, Yajurveda, Samaveda, and Atharvaveda—are considered the most sacred texts in Hinduism, with "Veda" literally translating to "knowledge.