Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent Persons, who are yet distinct One from Another. These three are one [thing], not one [Person], as it is said, 'I and my Father are One,' in respect of unity of substance not singularity of number.
TertullianThe angels as the guardians of men are set over men as instructors and monitors. This shows the relationship that is to exist between them. Man's attitude is to be one of obedience and subjection. He is to follow the lead of the angels, and consequently some reverence is already implied in the very relationship that exists between man and angel.
Tertullian