This can be stated in active form. AT: "when the apostles and elders dismissed the four men" or "when the believers in Jerusalem sent them" (See: [[rc://en/ta/man/translate/figs-activepassive]])
The abstract noun "encouragement" can be expressed with the verb "encourage." AT: "because what the apostles and elders wrote encouraged them" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
# also prophets
Prophets were teachers authorized by God to speak for him. AT: "because they were prophets" or "who were also prophets"
# the brothers
"the fellow believers"
# strengthened them
Helping someone to depend even more on Jesus is spoken of as if they were making them physically stronger. (See: [[rc://en/ta/man/translate/figs-metaphor]])