For us Christians, blessings have taken on an even greater meaning through Christ who perfectly revealed to us the goodness and love of God. St. Paul wrote, "Praised be the God and Father of our Lord Jesus Christ, who has bestowed on us in Christ every spiritual blessing." Jesus blessed those He encountered: the little children (Mark 10:13-16) and the apostles at the ascension (Luke 24:50-53). He blessed objects: the loaves used to feed the 5000 (Mark 6:34ff) and the bread at the Last Supper (Matthew 26:26-30). Since Christ entrusted His saving ministry to the Church, it has instituted various blessings for people as well as objects to prompt the faithful to implore God's protection, divine assistance, mercy, faithfulness, and favor.
Who can do a blessing? The Catechism states, "Every baptized person is called to be a 'blessing,' and to bless. Hence lay people may preside at certain blessings; the more a blessing concerns ecclesial and sacramental life, the more is its administration reserved to the ordained ministry (bishops, priests, or deacons)" (#1669). Priests are the ordinary ministers of blessings, asking God's help for those people being blessed or dedicating something to a sacred service; the priest's blessing is imparted with the weight of the Church and therefore has great value in the eyes of God. The blessing of a layperson upon another, such as a parent blessing a child, is an act of goodwill whereby the person implores God's aid for the person; the value of this blessing in the eyes of God depends upon the person's individual sincerity and sanctity.
A constitutive blessing, invoked by a bishop, priest, or deacon, signifies the permanent sanctification and dedication of a person or thing for some sacred purpose. Here the person or object takes on a sacred character and would not be returned to non-sacred or profane use. For example, when religious sisters or brothers profess final vows, they are blessed, indicating a permanent change in their lives. Or, when a chalice is blessed, it becomes a sacred vessel dedicated solely to sacred usage.
In all, in bestowing His own blessing, God declares His goodness. We in turn bless God by praising Him, thanking Him for all of His benefits, and offering to Him our service, adoration, and worship. When we invoke God's blessing, we implore His divine beneficence, trusting that He will respond to our needs.