Dearly loved ones, as I was very eagerly planning to write to you about the salvation we share in common, I felt it necessary [instead] to write urging you to contend earnestly for the faith [i.e., the teaching of Christ] which was once and for all delivered [by the apostles, See verse 17] to the saints [i.e., God's holy people].

But you dearly loved ones, you should remember the message that was previously told to you by the apostles of our Lord Jesus Christ,

But, you dearly loved ones, build yourselves up [spiritually] on [the foundation of] your most sacred faith; pray in [the power of] the Holy Spirit.