三思而行的英文：
[Literal Meaning]
three/think/aux./act
to think thrice before you act

[解释]
指经过反复考虑，然后再行动。

[Explanation]
to think carefully before one acts

[例子]
这么重要的亊情一定要三思而行，否则后悔就晚了。

[Example]
For such an important matter, we must think twice before we act, otherwise it will be too late for us to regret.

[英文等价词]
Look before you leap.
Think twice before you act.
Second thoughts are best.

see before you go
三思而行

"Look before you leap" is a familiar expression.
三思而行是一个很通俗的说法。

Look before you leap. —— Aesop
深思熟虑而后行。(三思而行)——伊索

She performed her promise of being discreet to admiration.
她三思而行，出色地履行了诺言。

You should think twice about employing someone you have never met .
你要雇用素未谋面的人应三思而行。

Anyone who is tempted to fly in the face of discretion had better think twice
任何打算贸然行事者，最好三思而行。