John Calvin Commentary Jeremiah 16:8

"And thou shalt not go into the house of feasting to sit with them, to eat and to drink." — Jeremiah 16:8 (ASV)

Here the Prophet refers to other feasts, where great joy prevailed. The meaning, then, is that the people were consigned to destruction, so that it was best to stay as far away from them as possible. Therefore, Jeremiah is forbidden to go to them at all, so that he would not associate with them in either joy or sorrow. It was as if he had been told: ‘Have nothing more to do with this people. If they lament their dead, leave them, for they are unworthy of any kindness. And if they hold joyful feasts, stay far from them, for all interaction with them is accursed.’ So, we now understand why the Prophet spoke of grief, lamentation, and mourning, and then mentioned joy. He adds afterward.