Cite the scanned version of the original dicionary like this:
Bosworth, Joseph. "níd-behéfe." An Anglo-Saxon Dictionary: Based on the Manuscript Collections of the Late Joseph Bosworth. Ed. Thomas Northcote Toller. Oxford: Clarendon Press, 1898. 717.
.Add:I.necessary :-- Nédbehéfe ys þá gyltas forceorfan necessarium est ipsas culpas succidere, Scint. 8, 4. Þ̵ is nýdbehéfe, Chrd. 111, 6. II. with dat. of person :-- Ús ys þín líf nýdbehéfe gít, Hml. 8. 22, 226: 28, 142: Scint. 8, 4. II a. with dat. of person and dat. infin. :-- Is lenctentíd eallum Crístenum mannum nédbehéfe tó gehealdenne, Wlfst. 102, 13.