This mystery is great (to musthrion touto mega estin). For the word "mystery" see Genesis 1:9 . Clearly Paul means to say that the comparison of marriage to the union of Christ and the church is the mystery. He makes that plain by the next words. But I speak (egw de legw). "Now I mean." Cf. 1 Corinthians 7:29 ; 1 Corinthians 15:50 . In regard of Christ and of the church (ei Criston kai [ei] thn ekklhsian). "With reference to Christ and the church." That is all that ei here means.