The definite article (lit. ‘the washing in [the] water’) may well
indicate a specific event, and the readers are scarcely likely to have taken
this as anything other than a reference to their experience of baptism. In 1
Cor 6:11 washing and sanctifying occur together as metaphors of salvation, with
an allusion to baptism highly probable. But here, the explicit mention o water
suggests not simply an extended metaphor for salvation but a direct reference
to water baptism, not to baptism by the Spirit . . . the language of ‘the
washing with water’ is likely to have a secondary connotation the notion of the
bridal bath. This would reflect both Jewish marital customs with their
prenuptial bath and the marital imagery of Ezek 16:8-14 which stands behind
this passage. In Ezek 16:9 Yahweh, in entering his marriage covenant with
Jerusalem, is said to have bathed her with water and washed off the blood from
her. (Andrew T. Lincoln, Ephesians [Word
Biblical Commentary; Dallas: Thomas Nelson, 1990], 375)