Question: "Why is the dove often used as a symbol for the Holy Spirit?"
Answer: All four Gospel accounts refer to the baptism of Jesus by John at the Jordan river (Matthew 3:16; Mark 1:10; Luke 3:22; John 1:32). The Luke account says “And the Holy Spirit came down in a bodily shape, like a dove on Him.” Because the Holy Spirit is just that—spirit—He is not visible to us. This occasion, however, was a real visible appearance, and was doubtless seen by the people. The dove is an emblem of purity and harmlessness (Matthew 10:16), and the form of the dove was assumed on this occasion to signify that the Spirit with which Jesus would be endowed would be one of purity and innocence.
Another symbol involving the dove comes from the account of the Flood and Noah’s ark in Genesis 6-8. When the earth had been covered with water for some time, Noah wanted to check to see if there was dry land anywhere, so he sent out a dove which came back with an olive branch in her beak (Genesis 8:11). Since that time, the olive branch has been a symbol of peace. Symbolically, the story of the dove tells us that God declared peace with mankind after the Flood purged the earth of its wickedness. The dove represented His Spirit bringing the good news of reconciliation with God. Of course, this was only in a temporal sense because true spiritual reconciliation with God only comes through Jesus Christ. But it is significant that the Holy Spirit was pictured as a dove at Jesus’ baptism, thereby once again symbolizing peace with God.
The Holy Spirit, when He assumes a visible form, assumes that which will be symbolic of the thing to be represented. At Pentecost, He assumed the form of “tongues of fire” (Acts 2:30) to signify the miraculous powers of language with which the apostles would be endowed and the power of their message. In the same way, His appearance as the dove symbolizes the gentle Savior bringing peace to mankind through His sacrifice.