See M'Clellan and Tregelles _ad loc_.
'Tatian here speaks of God and not of the Logos, and in this respect, as well as language and context, the passage differs from the fourth Gospel' [Endnote 306:1], &c.

Nevertheless it may safely be left to the reader to say whether or not it was taken from it.
The Epistle of the Churches of Vienne and Lyons contains the following:-- _Ep.Vienne.et Lugd_.Sec.

iv.
Thus too was fulfilled that which was spoken by our Lord; that a time shall come in which every one that killeth you shall think that he offereth God service.
[Greek: Eleusetai kairos en o pas ho apokteinas humas doxei latreian prospherein to Theo.] _John_ xvi.

2.
Yea, the hour cometh, that every one that killeth you will think he offereth God service.
[Greek: All' erchetai hora hina pas ho apokteinas humas, doxae latreian prospherein to Theo.] It is true that there are 'indications of similar discourses' in the Synoptics, but of none containing a trait at all closely resembling this.

The chances that precisely the same combination of words ([Greek: ho apokteinas humas doxei latreian prospherein to Theo]) occurred in a lost Gospel must be necessarily very small indeed, especially when we remember that the original saying was probably spoken in Aramaic and not in Greek [Endnote 307:1].
Dr.Keim, in the elaborate monograph mentioned above, decides that Celsus made use of the fourth Gospel.