Guardian Angels
An early Christian theologian known as Origen first popularized the idea of a guardian angel and a devil assigned to every soul.
In his work ‘Origen de Principiis’ chapter 8 he states ‘All of which things were disposed, as I have said, not indiscriminately and fortuitously, but by a most appropriate and just decision of God, who arranged them according to deserts, in accordance with His own approval and judgment: so that to one angel the Church of the Ephesians was to be entrusted; to another, that of the Smyrnaeans; one angel was to be Peter’s, another Paul’s; and so on through every one of the little ones that are in the Church, for such and such angels as even daily behold the face of God must be assigned to each one of them; and there must also be some angel that encampeth round about them that fear God.’
This along with other quotes are what started the doctrine of guardian angels. For scripture, Origen sites the following references:
Mat 18:10 Take heed that ye despise not one of these little ones; for I say unto you, That in heaven their angels do always behold the face of my Father which is in heaven.
Psa 34:7 The angel of the LORD encampeth round about them that fear him, and delivereth them.
Of course, I personally don’t feel there is one guardian angel assigned to every human, but rather that God will send guardian angels when a person is in need of that kind of protection.