有备无患，汉语成语，字面意思是“where there is precaution, there is no danger”，表示事先有准备，就可以避免祸患。可以翻译为“readiness is all，have a second string to one's bow”等。

例句：

你最好带把伞，有备无患。

You'd better take an umbrella just in case.