John 6:69

69.And we have believed and known. The verbs are in the past tense, but they may be changed into the present tense, we believe and know, but it makes little difference in the meaning. In these words Peter gives a brief summary of faith. But the confession appears to have nothing to do with the matter in hand, for the question had been raised about eating the flesh of Christ. I reply, although the twelve did not at once comprehend all that Christ had taught, yet it is enough that, according to the capacity of their faith, they acknowledge him to be the Author of salvation, and submit themselves to him in all things. The word believe is put first, because the obedience of faith is the commencement of right understanding, or rather, because faith itself is truly the eye of the understanding. But immediately afterwards knowledge is added, which distinguishes faith from erroneous and false opinions; for Mahometans and Jews and Papists believe, but they neither know nor understand any thing. Knowledge is connected with faith, because we are certain and fully convinced of the truth of God, not in the same manner as human sciences are learned, but when the Spirit seals it on our hearts.