According to Matthew 3:16, during the Baptism of Jesus the Holy Spirit descended like a dove and came to rest on Jesus. For this reason the dove became a symbol of the Holy Spirit and in general it occurs frequently in connection with early representations of baptism. It signifies also the Christian soul, not the human soul as such, but as the presence of the Holy Spirit.
However the more ancient explanation of the dove as a Christian symbol refers to it as a symbol of Christ. In the 2nd century it was explained that the number 801 is both the numerological value of the sum in Greek of the letters of the word "dove" (Greek: περιστερά) and the sum of the values of the letters Alpha and Omega, which refers to Christ. In the Bible story of Noah and the Flood, after the flood a dove returns to Noah bringing an olive branch as a sign that the water had receded, and this scene recalled to the Church Fathers Christ who brings salvation through the cross. This biblical scene led to interpreting the dove also as a symbol of peace.