“Purify me, Lord, and cleanse my heart so that, washed in the Blood of the Lamb, I may enjoy eternal bliss.”
(Vesting prayer while putting on the alb).
The alb is a full length white garment worn by priests and deacons, and altar servers while performing their duties on the sanctuary. As with other vestments its origin goes back to the basic robe of classical Rome and it was tradition at that time for newly baptised Christians, who were mainly adults, to wear a white garment as a sign of their reception into the church. This is why babies are wrapped in a white garment when they are baptised today.
The alb also recalls the Lord’s Transfiguration when His clothes became dazzlingly white.
"There in their presence he was transfigured: his face shone like the sun and his clothes became as dazzling as light." Matthew 17, 2.
"his clothes became brilliantly white, whiter than any earthly bleacher could make them." Mark 9, 3.
What we do during the Mass is a foretaste of our life in heaven and in his vision of heaven St. John describes seeing a vast number, impossible to count, dressed in white robes and praising God.
For a priest the alb is a symbol of the quest for a purity of conscience.
(The greyness of the alb in the picture is due to shadows falling on it when the picture was taken.)