en_tn/act/01/15.md

In those days

"In those days shortly after Jesus went back to heaven"

in the midst of the brothers

"brothers" often refers to fellow believers and would include both men and women.

It was necessary that the scripture should be fulfilled

Peter is specifically addressing the prophecies that related to Judas.

by the mouth of David

"the words of David." The word "mouth" is used to refer to "words" even though David wrote them. (See: rc://en/ta/man/translate/figs-metonymy)