“A stumbling block before the blind”
You must not curse the deaf or place a stumbling block before the blind, but you shall fear your God. (Leviticus 19:14 BSB)
What it sounds like today
A basic rule against being mean to disabled people.
The cultural key
On the surface this forbids cruel pranks, mocking someone who cannot hear you or tripping someone who cannot see the obstacle, acts whose special cowardice is that the victim cannot defend themselves, which is why God adds 'but you shall fear your God' (He sees what the victim cannot). But the phrase 'a stumbling block before the blind' was quickly understood far more broadly. It became a governing ethical principle against exploiting anyone's ignorance or vulnerability: giving bad advice to someone who trusts you, setting a trap for the naive, deliberately tempting a person into wrongdoing, or profiting from another's blind spot. 'Placing a stumbling block' came to name the whole family of sins that take advantage of what another cannot see. The New Testament uses 'stumbling block' the same way, warning against causing a weaker believer to fall. A modern reader sees a simple kindness rule; the first hearers heard a wide principle against exploiting the helpless and misleading the trusting.
Recovered meaning
The literal ban on tormenting the deaf and blind became a broad principle: never exploit another's blind spot, mislead the trusting, or lead someone into harm or sin. 'A stumbling block before the blind' names the whole family of sins that prey on what others cannot see.