The phrase “let me sleep on it” means to take some time to think about a decision or a problem before making a final choice or commitment. It suggests that the person wants to reflect on the matter overnight (or for a period of time) in order to gain clarity or perspective, rather than making a hasty decision. This expression highlights the importance of contemplation and the idea that sometimes a fresh perspective can emerge after a good night’s rest. It is often used in both personal and professional contexts when discussing important decisions.