Saul and Barnabas are both sent to Jerusalem, possibly in keeping with the idea that two witness are required to establish the truth of a matter (see Deuteronomy 19:15; John 8:17). They would thus not only bring money but also give testimony regarding the church in Antioch. It may also have been for the sake of wisdom; finances should never be in the hands of one person only. Most likely this visit from Saul is the same visit as the one which he mentions in Galatians 2:1–10.1
30 And they did so, sending it to the elders by the hand of Barnabas and Saul.