Here is what this chapter of the Manu Smriti recommends:

  1. A man, aged thirty years, shall marry a maiden of twelve who pleases him, or a man of twenty-four a girl eight years of age; if (the performance of) his duties would (otherwise) be impeded, (he must marry) sooner.

Bhishma says much the same thing in this chapter of the Anushasana Parva of the Mahabharata:

A person of thirty years of age should wed a girl of ten years of age called a Nagnika. Or, a person of one and twenty years of age should wed a girl of seven years of age.

Note that these recommendations are more binding for the lower bound rather than the upper bound. Here is what the Mahabharata translator says in a footnote:

Nagnika is said to be one who wears a single piece of cloth. A girl in whom the signs of puberty have not appeared does not require more than a single piece of cloth to cover her. The mention of Nagnika, the commentator thinks, is due to an interdiction about wedding a girl of even ten years in whom signs of puberty have appeared.

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