Acts 15:22 identifies Judas and Silas as the chosen messengers—the same men sent here to deliver the letter orally.

Acts 15:25 records the decision to send Judas and Silas — here they are actually sent, so it's the same action.

Acts 17:4 shows Silas later ministering with Paul in Thessalonica — the same Silas sent from Jerusalem here.

1 Thessalonians 1:1 identifies Silas (Silvanus) as a co-author with Paul — the same Silas sent here.