The Evangelist states three times that the disciples did not comprehend this prediction. They regarded His words as having some unusual and hidden meaning. They understood not a single word of these sayings, for they reasoned thus: This man performs so many miracles, He raises the dead, He gives the blind their sight, etc., from all of which it is evident that He will yet become a person of high position, for it is plain that God is with Him. Besides this, the Scriptures declare of Him that He shall have a glorious kingdom and exercise dominion over kings and princes on earth, while we, His servants, will also become princes and great lords. For who could in the least injure such a Person, who controls death and cures all infirmities with a single word? If He so desires, He can make the heathens His subjects and put beneath His feet all His enemies. Hence they dame to the conclusion that God loves Him too much to suffer any harm to befall Him; His sayings in regard to His sufferings and death must surely have another meaning. Thus reasoned the apostles in their simplicity.
God’s works are indeed incomprehensible, if they are considered before they are accomplished, but as soon as they are finished they are perfectly plain and intelligible. St. John states repeatedly that the disciples did oftentimes not understand the words of Christ, until the acts to which they referred had been accomplished. It is therefore necessary to have faith in the Word of God when He speaks He refers to matters far beyond the power of our comprehension; hence it behooves us to believe what He says, and then we shall fully experience and understand the true meaning of His words. (Luther’s House Postil, Sermon for Sexagesima, Volume 1, p. 218-219)