The notion of beings who have a purely spiritual existence is common to many religious systems. Angels belong to this category in the Judaeo-Christian tradition. In the Old Testament, angels are somewhat ill-defined beings, whose primary task is to act as messengers and envoys of God. Among their tasks are the protection and support of those who are faithful to God (e.g. in the escort of the Israelites from Egypt - Exodus 23:20; cf. Psalm 91:11). In the period between the Old and New Testaments, the categories and functions of angels became much more precisely defined, and many elements of this development can be seen in the New Testament writings.
The idea that each person has a guardian angel is a very ancient, popular one in both pagan and Jewish tradition. It is reflected in Jesus’ reference to the angels who protect the children (Matthew 18:10) and in the reference to the assumption that Rhoda saw Peter’s angel rather than Peter himself (Acts 12:15). This conception was given more formal definition in the Middle Ages by various theologians, including Thomas Aquinas. Pseudo-Dionysius, the sixth century mystical theologian, laid the foundation for the speculative classification of angels into hierarchies.
The guardian angels were originally commemorated with St Michael. They were first given a day of their own in Portugal in the sixteenth century, and the idea was extended to the whole of the Roman Catholic Church by Pope Clement X in 1670.
For Liturgical Use
The idea that each person has a guardian angel is a very ancient, popular one in both pagan and Jewish tradition. It can be seen in Jesus’ reference to the angels who watch over children and also in Peter’s escape from prison in Acts 12. The idea was given much more formal definition in the Middle Ages, and a special day was given to the guardian angels in 1670.
Bless the Lord, you angels of the Lord, bless the Lord, all you heavenly hosts.