tn “Before it” means before the deity in the form of the calf. Aaron tried to redirect their worship to Yahweh, but the people had already broken down the barrier and were beyond control (U. Cassuto, Exodus, 413).
sn The word is חַג (khag), the pilgrim’s festival. This was the word used by Moses for their pilgrimage into the wilderness. Aaron seems here to be trying to do what Moses had intended they do, make a feast to Yahweh at Sinai, but his efforts will not compete with the idol. As B. Jacob says, Aaron saw all this happening and tried to rescue the true belief (Exodus, 941).