en_tn/act/01/21.md

General Information:

Here the word "us" refers to the apostles and does not include the audience to whom Peter is speaking. (See: rc://en/ta/man/translate/figs-exclusive)

Connecting Statement:

Peter finishes his speech to the believers that he began in Acts 1:16.

It is necessary, therefore

Based on the scriptures that he quoted and on what Judas had done, Peter tells the group what they must do.

one of the men who accompanied us ... must be a witness with us of his resurrection

Peter lists the qualifications for the man who is to replace Judas as an apostle.

the Lord Jesus went in and out among us

Going in and out among a group of people is a metaphor for openly being part of that group. AT: "the Lord Jesus lived among us" (See: rc://en/ta/man/translate/figs-idiom)