Sleep on it

Examples:
1. Thanks for your job offer but I need some time to think about it. Let me sleep on it and I'll give you an answer tomorrow.
2. He told me he'd have sleep on it before he could agree to my request for a pay rise.
3. We couldn't decide which car to buy so we decide to sleep on it - we didn't want to buy the wrong one.
See on http://www.bbc.co.uk