A-séðan

According to the Old English Dictionary:

a-séðan

p. -séððe; pp. -séðed To affirm, confirm; affirmare, con-firmare :-- Sume [adverbia] syndon ad vel confirmativa, mid ðám we aséðaþ úre spræce some adverbs are affirmative or confirmative, with which we affirm our speech, Ælfc. Gr. 38; Som. 40, 16. a-seðan