In plain words
It has no mark to know it by and no ending. It is peace through and through. It shines beyond every object and is never approached as something to be known. Neither imagining nor doubt can reach it. That alone I am. Of this there is no doubt.
Word for word
Without identifying marks, imperishable and utterly peaceful, shining beyond objects, not approached as a knowable object and not reached by conception or doubt: that alone am I. There is no doubt in this.