The white gown
The white dress symbolizes purity of heart and life for which Chris will be responsible in the life of Beth.
Husbands, love your wives, just as Christ also loved the church and gave Himself for her, that He might sanctify and cleanse her with the washing of water by the word, that He might present her to Himself a glorious church, not having spot or wrinkle or any such thing, but that she should be holy and without blemish. So husbands ought to love their own wives as their own bodies; he who loves his wife loves himself. Ephesians 5:25-28