“When [Barnabas] arrived and saw the undeserved kindness of God, he rejoiced and began to encourage them all to continue in the Lord with heartfelt resolve.”
~Acts 11:23

The early Christian congregation was changing in the sense that it was no longer exclusive to Jews or Jewish proselytes.
Barnabas was a Levite who had converted to Christianity. (Acts 4:36)
He was appointed an apostle because holy spirit moved him to do missionary work. (Acts 13:4; 14:14)
When he saw the enthusiasm with which the new converts in Antioch received the good news of the kingdom, he sought out Paul and together they helped strengthen the congregation. (Acts 11:25,26)
It was there that “by divine providence” Christ’s disciples were first called “Christians.”
In Greek, the phrase translated “heartfelt resolve” literally means “purpose of the heart.”
Other synonyms could be: firmness, conviction, determination.
Barnabas not only told his new spiritual family to stay in the truth; he took them under his wing and nurtured their faith.
Through personal sacrifice, tolerance toward others, and a joyous spirit, he exemplified ‘continuing in the Lord with heartfelt resolve.’