פירוש על קידושין 65:4

The Talmud cites a source that refers to the farmers bringing their first fruits to Jerusalem. As they enter the city, artisans stand before them and greet them. This implies that artisans are allowed to stop working to stand up in honor of other people coming through.
The resolution is that artisans can stop working to greet the farmers going to the Temple, but they may not do so to greet sages.