He made known to us the mystery of his will according to his good pleasure, which he purposed in Christ (NIV)
Making known to us the mystery (secret) of His will (of His plan, of His purpose). [And it is this:] In accordance with His good pleasure (His merciful intention) which He had previously purposed and set forth in Him (AMP)
Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself: (KJV)