Adam Clarke on Luke 6:13

He chose twelve - Εκλεξαμενος απ' αυτων, He chose twelve Out of them. Our Lord at this time had several disciples, persons who were converted to God under his ministry; and, out of these converts, he chose twelve, whom he appointed to the work of the ministry; and called them apostles, i.e. persons sent or commissioned by himself, to preach that Gospel to others by which they had themselves been saved. These were favored with extraordinary success:

1. Because they were brought to the knowledge of God themselves.

2. Because they received their commission from the great Head of the Church. And

3. Because, as he had sent them, he continued to accompany their preaching with the power of his Spirit.

These three things always unite in the character of a genuine apostle. See on Mat 10:1-4 (note).