What is the authenticity of the saying: "O You whom eyes do not behold, nor conjectures mingle with, nor describers describe"?

The Prophet (peace be upon him) passed by a Bedouin who was supplicating to Allah with great praise. He asked about him, and when the Bedouin was brought to him, he gifted him gold that had been given to him (the Prophet), saying that he had given it to him because of his excellent praise of Allah.