I intend is in the future tense in the Greek; this is reflected in Good News Translation “I will always remind you” (and see also New English Bible “I will not hesitate to remind you”). A translation should be avoided that excludes this letter, that is, one which gives the idea that Peter will in the future remind his readers by writing yet another letter. A more appropriate way of understanding the future tense here is in the sense of including the present: “I will always remind you, as I am doing now.” In this sense New Revised Standard Version is quite appropriate: “I intend to keep on reminding you.” We can also express this sentence as “I will continually bring these matters to your attention” or “I will continually cause you to remember these things.” In some languages there will be idioms that will capture this meaning quite satisfactorily; for example, the English idiom “jog your memory.”

These things refers back to verses 3-11, which contain a summary of Peter’s message and of the apostolic message in general.

You know them refers back to The First Letter from Peter, which forms a background to The Second Letter from Peter and which the readers are assumed to have read. Many of the things discussed in 2 Peter are also found in 1 Peter, such as the importance of being steadfast (1 Peter 1.3-9) and the possibility of sharing in divine glory (1 Peter 1.8; 5.1).

Are established translates a verb that indicates solid grounding in and firm commitment to something, as in Good News Translation “firmly grounded,” and New English Bible “well grounded.” Are established in many languages can be rendered as “are deep in your heart” or “are firmly fixed in your heart.” The truth that you have refers to the Christian message that the believers have been taught since their conversion and baptism. Truth is often used in the New Testament to designate the Christian message in general (see, for instance, Gal 2.5; Eph 1.13; Col 1.5; 2 Thes 2.12-13; 2 Tim 2.15; James 1.18). Here we can see the development of a body of authoritative Christian teaching to which believers have to give their allegiance. This truth that the believers have is something they received as a result of proclamation and teaching (New Revised Standard Version “the truth that has come to you”); it was handed down to them through the Christian community’s ministry of preaching and nurture. Some translators may be able to follow New Revised Standard Version “that has come to you.” However, in certain languages it will be difficult to talk about an abstract idea such as truth performing an action, that is, “coming.” In this case we can say “you heard the true teachings” or “the true teachings were preached (or, taught) to you.”

An alternative translation model for this verse is:
• Therefore I will continually cause you to remember those things, even though you know them already. The true teachings that were taught to you are also firmly fixed in your heart (or, mind).

Quoted with permission from Arichea, Daniel C. and Nida, Eugene A. A Handbook on The Second Letter from Peter. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .