That he might sanctify it (ινα αυτην αγιαση). Purpose clause with ινα and the first aorist active subjunctive of αγιαζω. Jesus stated this as his longing and his prayer (John 17:17-19). This was the purpose of Christ's death (verse Ephesians 5:25).

Having cleansed it (καθαρισας). First aorist active participle of καθαριζω, to cleanse, either simultaneous action or antecedent.

By the washing of water (τω λουτρω του υδατος). If λουτρον only means bath or bathing-place ( = λουτρον), then λουτρω is in the locative. If it can mean bathing or washing, it is in the instrumental case. The usual meaning from Homer to the papyri is the bath or bathing-place, though some examples seem to mean bathing or washing. Salmond doubts if there are any clear instances. The only other N.T. example of λουτρον is in Titus 3:5. The reference here seems to be to the baptismal bath (immersion) of water, "in the bath of water." See 1 Corinthians 6:11 for the bringing together of απελουσασθε and ηγιασθητε. Neither there nor here does Paul mean that the cleansing or sanctification took place in the bath save in a symbolic fashion as in Romans 6:4-6. Some think that Paul has also a reference to the bath of the bride before marriage. Still more difficult is the phrase "with the word" (εν ρηματ). In John 17:17 Jesus connected "truth" with "sanctify." That is possible here, though it may also be connected with καθαρισας (having cleansed). Some take it to mean the baptismal formula.