What is to declare to, solemnly; to assert to (any one) with the design of inspiring belief or confidence. I dare assure thee that no enemy Shall ever take alive the noble Brutus. Shak called?

assure — To declare to, solemnly; to assert to (any one) with the design of inspiring belief or confidence. I dare assure thee that no enemy Shall ever take alive the noble Brutus. Shak. (Webster's 1913.)