Charles Ellicott Commentary Psalms 81:9

"There shall no strange god be in thee; Neither shalt thou worship any foreign god." — Psalms 81:9 (ASV)

Open ... —A condensed statement of God’s gracious promise (Deuteronomy 7:12–13; Deuteronomy 8:7; Deuteronomy 8:9; Deuteronomy 11:13; Deuteronomy 11:16, and others). It is said to have been a custom in Persia that when the king wishes to do a visitor special honour, he desires him to open his mouth wide, and the king then crams it full of sweets, and sometimes even with jewels. And to this day, it is a mark of politeness in Eastern cultures to tear off the daintiest bits of meat for a guest, and either lay them before him or put them in his mouth. (See Thomson, Land and Book, p. 127.)