Was Mahli a son of Levi, or his grandson through Merari?

Mahli was Merari’s son and Levi’s grandson, and Ezra does not say otherwise. Hebrew ben, ‘son’, is used of any descendant, and Ezra is not giving Mahli’s father but showing which tribe the newcomers belonged to. The man brought to Ezra was one “of the sons of Mahli”, that is, of the Levite clan named after Mahli, “the family of the Mahlites” (Numbers 3:33). That clan, in turn, belonged to Levi, the son of Jacob, or Israel. Keil and Delitzsch explain the verse in exactly this way: Mahli, ‘the son, i.e., grandson, of Levi’.

The context shows why Ezra names Levi and passes over Merari. When Ezra gathered the returning exiles by the river Ahava, he “found there none of the sons of Levi” (Ezra 8:15), so he sent for Levites to serve in the temple. What mattered was that these men were true Levites, and the phrase says so. The book of Ezra uses ‘son of’ in this long sense elsewhere too. Ezra himself is “Ezra the son of Seraiah” (7:1), though the chief priest Seraiah was put to death at Riblah when Jerusalem fell (2 Kings 25:18–21), well over a century before Ezra came to Jerusalem; the line is shortened, as Hebrew genealogies often are.

A later Mahli

There was a second Mahli, the son of Mushi and grandson of Merari (1 Chronicles 6:47). If Ezra means his line, the point is the same: Mahli was a descendant of Levi, not his son.