Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Synods of Sardica, Carthage, Constantinople, and Carthage Under St. Cyprian, Which Canons Were Received by the Council in Trullo and Ratified by II. Nice.: Canon LXXII

Canon LXXII.  (Greek lxxv.)

Of the baptism of infants when there is some doubt of their being already baptized.

Item, it seemed good that whenever there were not found reliable witnesses who could testify that without any doubt they were baptized and when the children themselves were not, on account of their tender age, able to answer concerning the giving of the sacraments to them, all such children should be baptized without scruple, lest a hesitation should deprive them of the cleansing of the sacraments.  This was urged by the Moorish Legates, our brethren, since they redeem many such from the barbarians.

Notes.

Ancient Epitome of Canon LXXII.

It seemed good that they should be baptized about whom there was an ambiguity whether they had been baptized or no; lest they might through that doubt lose the divine ablution.

This is Canon vij. of Carthage, September, a.d. 401.