He breathed on them - It was customary for the prophets to use some significant act to represent the nature of their message. See Jeremiah 13; Jeremiah 18, etc. In this case the act of breathing was used to represent the nature of the influence that would come upon them, and the source of that influence. When man was created, God breathed into him the breath of life, Genesis 2:7. The word rendered “spirit” in the Scriptures denotes wind, air, breath, as well as Spirit. Hence, the operations of the Holy Spirit are compared to the wind, John 3:8; Acts 2:2.
Receive ye the Holy Ghost - His breathing on them was a certain sign or pledge that they would be endowed with the influences of the Holy Spirit. Compare Acts 1:4; John 2.