Ephesians 5:14 - a baptism hymn?

 In response to our latest video on Romans, 

@christianmichael8609 comments:@23:10 - that is a strong statement there - that the recipients of the Apostolos letters did not know of Christian initiation by baptism. Ought you not be more cautious? Laodiceans 5.14 is explicitly cited by Epiphanius, and as you surely know reputable scholars have suggested that this was a baptismal initiation saying.
My reply: With your question you confirm my statement. Reputable scholars are reading Ephesians 5.14 in the light of the canonical 14-Letter Collection and the canonical NT, particularly Rom. 6:3-4 (Bruce, for example), where, of course such light-metaphor reminds of baptism. This is exactly the point, of what I was saying. Once you move, as you do, within the canonical frame, things are clear which are very different within the 10-Letter Collection. Jürgen Becker and Ulrich Lutz, for example, simply speak of Eph 5:14 as of a "baptismal song", yet, even in canonical Eph 5 there is no single mention of baptism. Hence they are careful in saying twice that this is a "guess" (in German they use twice "vermutlich", p. 166). Bruce is more willing to follow the idea, yet he makes a cautious note of B. Noack, “Das Zitat in Ephes. 5:14,” ST 5 (1951), 52-64, for its being primarily a resurrection hymn (although applicable secondarily to baptism) and points to R. P. Martin, “Aspects of Worship in the New Testament Church,” VE 2 (1963), 30. Bruce, however, refers to the earliest commentary that exists on this verse Eph 5:14 and writes (Bruce, Commentary ad loc.): "Attempts have been made to strengthen the identif ication of the tristich as a baptismal hymn by the argument that its rhythm is that found in the initiation formulae of various Hellenistic cults. The formula most commonly adduced is one quoted by Firmicus Maternus as uttered by the person newly initiated into the Attis mystery. Such formal parallels are difficult to establish, and throw no light on the meaning of what is, in context and content, an explicitly Christian composition. Clement of Alexandria quotes this tristich and accompanies it with another tristich amplifying the reference to Christ in its third clause." His criticism of referencing Hellenistic cults should have also led him to be more cautious with referencing Christian baptism, as Clement points to Christ, but does not know of a baptismal link, let alone of a baptismal hymn behind this text. Interesting is that Strack-Billerbeck adduce 1 Tim 2:8 - again, providing a non-baptismal context. So I would be less firm than you are. In addition, Makus Barth does not follow this "guess" in his commentary on Ephesians, if I have not overlooked something.