Earliest Iron References in India

The question asks to identify the earliest literary source mentioning iron in the Indian Sub-Continent.

Vedic Literature and Iron

The mention of iron ('ayas') appears in Vedic literature. However, the interpretation varies:

• Rigveda: Primarily uses the term 'ayas', which is generally understood to refer to copper or bronze in this context. Explicit references to iron are scarce or ambiguous.
• Yajurveda: Contains clearer references to iron ('syama ayas' - black metal, or 'krishna ayas' - dark metal), indicating its presence and use. This text marks a significant literary stage for iron references.
• Samaveda: Largely based on the Rigveda, it doesn't offer significantly earlier or clearer references to iron.
• Vinaya Pitaka: This Buddhist text is considerably later than the Vedic Samhitas and mentions iron, but not as the earliest reference.

Conclusion

Based on the available Vedic literature, the Yajurveda provides the earliest distinct literary references to iron in the Indian Sub-Continent, making it the correct choice.