Albert Barnes Commentary 1 Peter 5:13

"She that is in Babylon, elect together with [you], saluteth you; and [so doth] Mark my son." — 1 Peter 5:13 (ASV)

The church that is at Babylon, elected together with you. It will be readily seen that much of this is supplied by our translators; the words "church that is" are not in the original. The Greek is, h en babulwni suneklekth; and it might refer to a church or to a female.

Wall, Mill, and some others suppose that the reference is to a Christian woman, perhaps the wife of Peter himself (compare to 2 John 1:1). But the Arabic, Syriac, and Vulgate, as well as the English versions, supply the word church. This interpretation seems to be confirmed by the word rendered elected together with—suneklekth.

This word would be properly used in reference to one individual if writing to another individual, but would hardly be appropriate if applied to an individual addressing a church. Moreover, it could not readily be supposed that any one female in Babylon could have such prominence, or be so well known, that nothing more would be necessary to designate her than merely to say, "the elect female." Regarding the word Babylon here and the place it denotes, see the Introduction, section 2.

And so doth Marcus my son. Probably John Mark (see the notes on Acts 12:12 and Acts 15:37).

Why he was now with Peter is unknown. If this was the Mark referred to, then the word son is a title of affection and is used by Peter with reference to his own superior age. It is possible, however, that some other Mark may be referred to, in whose conversion Peter had been instrumental.