en_tn/1ki/02/12.md

sat on the throne of his father David

The throne represents the authority of the king. AT: "became king, as his father David had been" (See: rc://en/ta/man/translate/figs-metonymy)

his rule was firmly established

This can be translated in active form. AT: "Yahweh firmly established Solomon's rule" or "Yahweh caused Solomon to take complete control of the kingdom" (See: rc://en/ta/man/translate/figs-activepassive)