Origen eh? About fifty years before that we have Tertullian make the same claim that what he received was passed down; and also relates this to Baptism:
The Chaplet Chapter 3
If no passage of Scripture has prescribed it, assuredly custom, which without doubt flowed from tradition, has confirmed it.** For how can anything come into use, if it has not first been handed down?** Even in pleading tradition, written authority, you say, must be demanded. Let us inquire, therefore, whether tradition, unless it be written, should not be admitted. Certainly we shall say that it ought not to be admitted, if no cases of other practices which, without any written instrument, we maintain on the ground of tradition alone, and the countenance thereafter of custom, affords us any precedent.** To deal with this matter briefly, I shall begin with baptism**. When we are going to enter the water, but a little before, in the presence of the congregation and under the hand of the president, we solemnly profess that we disown the devil, and his pomp, and his angels. Hereupon we are thrice immersed, making a somewhat ampler pledge than the Lord has appointed in the Gospel.
And of course his beliefs on Baptism are as follows:
***But they whose office it is, know that baptism is not rashly to be administered. *
Give to every one who begs you, has a reference of its own, appertaining especially to almsgiving. On the contrary, this precept is rather to be looked at carefully…
…. And so, according to the circumstances and disposition, and even age, of each individual, the delay of baptism is preferable; **
principally, however, in the case of little children.
Another great argument that the early Church was baptizing children! For why would Tertullian address “the case of little children” being baptized, unless it was already an established practice?