Spend not where you may save; spare not where you must spend.

Understand the thought

Meaning in plain English

Avoid unnecessary spending, but do not refuse an expense that a real need requires. Good judgement distinguishes a useful saving from an economy that prevents the task from being done properly.

What the words are saying

The two instructions balance each other. The first encourages restraint where spending serves no worthwhile purpose; the second warns that reluctance to spend can become harmful when something essential is needed. The proverb therefore resists both indiscriminate expense and indiscriminate thrift. Its usefulness depends on identifying the actual need rather than calling every desired purchase necessary. It does not say that resources are always available for an essential cost. The practical question is what the task requires, what alternatives exist and whether saving at that point would undermine the purpose you are trying to achieve.

Everyday example

An exhibition team reuses sound display boards but replaces damaged supports rather than saving money by leaving the display unstable.

When to use it

Use it when deciding which costs are avoidable and which are necessary to a worthwhile purpose.

Agent-assisted editorial interpretation. This explains the words; it does not by itself verify their author or earliest origin.