The second commandment forbids every improper use of God’s name. Blasphemy is the use of the name of God, of Jesus Christ, of the Virgin Mary, and of the saints in an offensive way.
False oaths call on God to be witness to a lie. Perjury is a grave offence against the Lord who is always faithful to his promises.
“Do not swear whether by the Creator, or any creature, except truthfully, of necessity, and with reverence.”2
In Baptism, the Christian receives his name in the Church. Parents, godparents, and the pastor are to see that he be given a Christian name. The patron saint provides a model of charity and the assurance of his prayer.
Ps 8:1.
St. Ignatius of Loyola, Spiritual Exercises, 38.
Cf. Isa 43:1.