Save it spoken language
Said angrily to someone when you want them not to say something.
You're talking too much, nobody here wants to hear it. Save it!
A: "Hey, do you want to hear about..." B: "I've heard enough. Save it!"
A: "I swear I didn't kill anyone, you caught the wrong person" B: "We have all the evidence. Save it!"
The origin of this phrase is not clear.