Isaiah continues speaking to the people of Judah.

## when a holy feast is observed ##

AT: "when you observe a holy feast" (See: [[rc://en/ta/man/translate/figs-activepassive]])

## and gladness of heart ##

"and you will be glad"

## flute ##

See how you translated this in [Isaiah 5:11](../05/11.md).

## to the Rock of Israel ##

The refers to Yahweh and compares him to a rock because he protects his people. AT: "Israel's protective rock" or "who is like a protective rock for Israel."