“Faith like a grain of mustard seed… move this mountain”
Matthew 17:20
IdiomWell-supportedJesus
If you have faith the size of a mustard seed, you can say to this mountain, 'Move from here to there,' and it will move. Nothing will be impossible for you. (Matthew 17:20 BSB)
What it sounds like today
A literal promise of telekinesis that visibly doesn't happen.
The cultural key
Two idioms stacked. The mustard seed is again the proverb for the tiniest possible quantity. And 'uprooter of mountains' (oker harim) was a rabbinic epithet for a teacher who could resolve seemingly impossible interpretive difficulties; 'moving mountains' was already figurative speech for doing the impossible, the way we use it today ('move heaven and earth').
Recovered meaning
Not a physics claim: 'even the smallest real faith engages God's power with the genuinely impossible.' The contrast isn't small faith versus big faith; it's faith versus none, and a mustard seed's worth suffices.