Even though 3 Esdras does not fit into the area of Sacred Scripture (which has been dogmatically defined as a closed canon in the Council of Trent, so there’s no use arguing about it), apocryphal books do fit quite comfortably in Sacred Tradition, provided they are not heretical in nature. So books such as the ones within the Vulgate but have since been determined not to be Sacred Scripture (such books are 3&4 Esdras, Prayer of Manasses, 3 Maccabees, and Psalm 151) are relevant in Sacred Tradition; there are also apocryphal books surrounding the New Testament, but since the great majority are in fact heretical by nature, these heretical books do not render themselves well within Sacred Tradition, notable exceptions being the Protoevangelium of James (from where we get the traditions of Mary’s parents, Jesus’ grandparents, who are Joachim and Anne; as well as an early Christian witness to several Marian dogmas such as the Immaculate Conception) and another exception being the Acts of Peter (from where we get the account of Peter’s Martyrdom [even though this Acts of Peter is gnostic and therefore heretical, it does align itself to tradition in this regard and thus is a witness to early Christian, albeit a heretical Christian, to traditions such as these]).
By the very fact that it’s in the Vulgate shows that the early Church dearly loved this text, and quoted from it often {even Jesus Himself seems to quote 4 Esdras, when he says: ‘[H]ow often would I have gathered your children together as a hen gathers her brood under her wings, and you would not?’ (Lk 13:34 RSV-CE), and 4 Esdras says: ‘I gathered you as a hen gathers her brood under her wings’ (4 Esdras 1:30 RSV). I’m quite sure that the theme of ‘the hen gathering her brood under her wings’ was a widely used Semitic idiom; this theme nevertheless appears nowhere else within Sacred Scripture.}
