We have learnt the equivalence of the Buddha and the Dharma and how really seeing the Buddha implies really seeing the Dharma; ‘he who sees the Dharma, sees the Buddha' or 'he who sees the Buddha in his physical form does not really see the Buddha.' And this is said very clearly in the Diamond Sūtra. It is said that the Buddha is not to be perceived by means of his thirty-two marks. If you were to perceive the Buddha by means of his thirty-two marks then the Buddha would be indistinguishable from any universal monarch. According to the Buddhist tradition, the universal monarch is believed to possess thirty-two special marks, the same marks that a Buddha possesses. The Buddha cannot be perceived by his thirty-two marks. And it goes on saying that whoever sees the Buddha by his form or sees the Buddha by sound, he is mistaken, his footsteps on the path are perverted and he will never see the Buddha. So again the idea is that perceiving the Buddha by means of his physical form or body is not really perceiving the Buddha. The really perceiving of the Buddha is to perceive the Dharma, the transcendental dimension of the Buddhahood and not to see the Buddha by his physical dimension, by his worldly manifestation.
I would like to know, “he who sees the Dharma, sees the Buddha”, so he who sees the Buddha, does he see the Niravāna?
Something to add (补充两句）
This saying is not intend to be taken literally. It is used as a metaphor. Its object is to help explain the concept of duality in Mahayana Buddhism - between conventional (conditioning/human cognition) vs. ultimate (emptiness). In other words, seeing things as they really are. Let us not forget that the central theme of the Diamond Sutra is: that all dharmas are unreal and illusory.
Furthermore, the language used in the Diamond Sutra is not intended for those of immature or un-initiated mind and hence should not be understood only in its rudimentary forms.
Further reading: "The Diamond Sutra", William Gemmell, Kegan Paul, Trench, Trubner & Co Ltd, London. 1912.