Cite the scanned version of the original dicionary like this:
Toller, T. Northcote, and Joseph Bosworth. "ǽðan." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth : Supplement. Oxford: Clarendon Press, 1921. 22.
To overflow, deluge, lay waste :-- Cwæþ ðæt he wolde eall á ǽðan ðæt on eorþan wæs said that he would for ever lay waste all that was on the earth. Cd. 64; Th. 77, 24; Gen. 1280. v. éðan.