Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "in-siht." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 594.
, e : f. An account, narrative, argument :-- Onginneþ insiht æfter iohannem incipit argumentum secundum Johannem, Jn. Skt. p. 1, 1. [Goth. in-sahts narrative.]