The Catechism in Questions & Answers

422. When did the activity of the Apostle ministry begin in the church?

The activity of the Apostle ministry began on Pentecost. The ministry itself had already been given by Jesus Christ to His Apostles beforehand, however.

“Then He appointed twelve, that they might be with Him and that He might send them out to preach, and to have power to heal sicknesses and cast out demons.”
Mark 3: 14-16