Cite the scanned version of the original dicionary like this:
Bosworth, Joseph. "of-earmung." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth. Ed. Thomas Northcote Toller. Oxford: Clarendon Press, 1898. 729.
.Add :-- On ofearmunga and mildheortnesse in miseratione et misericordia, Ps. Rdr. 102, 5. Gemyne ofearmunga (miserationum) þínra and mildheortnesse þínre, 24, 6.