⟨ѯ⟩ and ⟨ѱ⟩ derived from Greek letters xi and psi, used etymologically though inconsistently in secular writing until the eighteenth century, and more consistently to the present day in Church Slavonic.

аз буки веди глаголь добро есть живете зело, земля, и иже и како люди мыслете наш он покой рцы слово твердо ук ферт хер цы червь ша ер ять ю