An Arabic proverb about a man who takes pity on his camel during a sandstorm and allows the animal to stick its nose under the side of the tent. The camel's head follows, then its neck and soon the whole animal is inside the tent, causing the Arab to be pushed out, into the storm.
This proverb is usually invoked in political debates when one side wants to warn others that if they allow one thing to happen, then many bad things will inevitablly follow; i.e. the slippery slope.