Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "beaftan." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 64.
, beaftian; p. beaftode, beafte, pl. beaftodon, beafton; pp. beaftod To lament; lamentare :-- We mid hondum beafton lamentavimus, Mt. Lind. Stv. 11, 17. v. beofian.