In some Eastern countries it was the custom that when a visitor called you invite them in.
If you would like them to stay a little while you offer them a drink. When the cup is half empty you refill it if you want them to visit longer. While you keep refilling the cup the visitor may stay, but when you stop refilling and the cup is empty it is time for them to go.
However, if you would like them to stay and live with you forever you keep on pouring until the cup overflows.
‘My cup overflows …………… and I dwell in the house of the Lord for ever.” Psalm 23