en_tn_lite_do_not_use/luk/02/42.md

they again went up

Jerusalem was higher than almost any other place in Israel, so it was normal for Israelites to speak of going up to Jerusalem.

at the customary time

"at the normal time" or "as they did every year"

the feast

This was another name for the Festival of the Passover, since it involved eating a ceremonial meal.