This verse describes the life of people who do not possess the qualities mentioned in verses 5-7. First of all, such people are blind and shortsighted. This combination may present some translation problems, since blind is stronger than shortsighted, and since obviously, if a person is blind, that person cannot be shortsighted at the same time. A better way of understanding this is to take shortsighted as having the effect of causing blindness: a shortsighted person is in effect blind, hence Good News Translation “is so shortsighted that he cannot see.” Furthermore this should not be taken literally but in a metaphorical sense, that is, being morally and spiritually blind; this metaphor is a popular one in the New Testament (see, for example, Matt 15.14; John 9.40-41; Rev 3.17). In many languages this metaphorical usage must be made clear by using a simile such as “is like a person who is so shortsighted that he cannot see.”

Secondly, these people have forgotten that they were cleansed from their old sins. Forgotten is literally “having received forgetfulness,” a typical Greek expression. The metaphor of cleansing from sin has its origin in the Old Testament, where it is connected with the Jewish sacrificial system. This metaphor was also widely used in the early church and is found in many parts of the New Testament (for instance, Titus 2.14; Heb 1.3; 9.14; 1 John 1.7, 9). Most commentaries are agreed that the reference here is to the purification that a person receives at baptism, during which a person is forgiven of his or her past sins before baptism. Baptism therefore signifies the end of the old and the beginning of the new: it marks a break between the old life of sin and disobedience and the new life of virtue and obedience to God. Many languages cannot literally translate the passive construction he was cleansed from his old sins but will need to name God as the one who does the cleansing, or else use a construction with a verb such as “receive.” In such cases this clause will be rendered “that God has cleansed him from his past (or, old) sins” or “that he has received from God cleansing from his past sins.” In still other languages it will be necessary to make a direct reference to baptism and say “that God has cleansed his past sins through baptism.”

An alternative translation model for this verse is:
• But whoever does not have these qualities is like a person who is so shortsighted that he cannot see (or, is blind), and has forgotten that God has cleansed him from his old sins.

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 .