seþan

Meaning

1. to prove

   Iċ eom ġeþafa þæs þe þū sæġst, for þon þe þū hit hæfst ġesēðed mid ġesċādwīslīcre race.

   I agree with what you're saying, since you have proven it with rational argument.

   late 9th century, King Alfred's translation of Boethius' The Consolation of Philosophy

2. to attest, affirm

   Eall hālgu ġewritu sēðaþ þæt sē is Hǣlend Crist.

   All the books of the Bible attest that he is Jesus Christ.

   c. 992, Ælfric, "The Nativity of St. James the Apostle"

Conjugation