“No one after lighting a lamp covers it with a jar”
No one lights a lamp and covers it with a jar or puts it under a bed. Instead, he sets it on a stand, so those who enter can see the light. (Luke 8:16 BSB)
What it sounds like today
Two generic images about visibility.
The cultural key
Hilltop limestone towns of Galilee gleamed pale in the sun, visible for miles; hearers could likely see one from where they sat. The lamp scene assumes a one-room peasant house: a single clay oil lamp on a stand lit the entire family. Covering it with the modios (a grain-measuring basket) would smother it, a deliberately absurd act. Behind both stands Israel's calling to be a light to the nations (Isaiah 42:6). Luke's absurdities are a jar and a bed instead of Matthew's grain-measure basket, and his lampstand shines for 'those who enter': the one-room Galilean house has quietly become a home with visitors and doorways, furniture translated for a wider world.
Recovered meaning
Being visible isn't optional for a disciple any more than a hilltop town can hide. Lighting a lamp and then smothering it defeats the whole point of lighting it.