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.
TertullianLearn about the incorruptible King, and know his heroes who never inflict slaughter on the peoples.
TertullianKeep always in mind the rule of faith which I profess and by which I bear witness that the Father and the Son and the Spirit are inseparable from each other, and then you will understand what is meant by it. Observe now that I say the Father is other [distinct], the Son is other, and the Spirit is other. This statement is wrongly understood by every uneducated or perversely disposed individual, as if it meant diversity and implied by that diversity a separation of Father, Son, and Holy Spirit
Tertullian