8:18 Chizkuni says that Leviim didn’t own land, so they would be free to concentrate on their tasks in the Temple. If they ploughed soil, their hands would be too coarse to play instruments.
I don’t understand this Chizkuni. Apart from teaching Torah, what did Leviim do when not officiating?
Similarly, when the Mishkan was settled in Shiloh for 369 years, it didn’t need to be carried. It was forbidden for the descendants of Merari who were responsible for carrying to become singers.
Also, the Leviim did own land around their cities. The restriction was that they could not own land elsewhere.
Learning and teaching torah is a full time occupation, and there is more than enough to learn to keep them busy their whole lives. Besides they had to be absolute experts in everything related to kodshim and taharos, and that can take plenty of time. The Chuzkuni was saying that they weren’t given land, not merely in order that they should plow, but that they shouldn’t be busy with any other work, and therefore they would devote themselves to H-shem’s avodas hakodesh, and in order that their fingers shouldn’t get thick, which would hamper their capacity to play the instruments. The fact that they could own land and could work the land is not his point, it is that they were meant to be devoted to avodas H-shem and had to be careful on the quality of their fingers. Regarding Merari, It seems that the Merari were allowed to sing even between ages 30-50, see Mizrachi Bamidbar 9-25.