living proof
noun [ S or U ]
be (the/a) living proof （用行动或品格）证明…属实
to prove that something is true by existing or having a particular quality
Reading his autobiography, you find he is living proof of the saying "truth is stranger than fiction". 读他的自传，你会发现他是“真相比小说更离奇”这句话的活生生的证明。
She is the living proof that you are never too old to change your life.
This scheme works, and these young people are living proof.