Countable and Uncountable: Pronounce husband and wife

[redgiant]

I pronounce this couple to be husband and wife. You may kiss.

In this sentence, there is no article and it is not "a husband and wife." Some books say without article, "husband and wife" is a abstract concept. Does the sentence mean "I pronounce this couple having the husband-and-wife relationship"?

What's wrong if I use "pronounce them to be a husband and wife" ?

I appreciate your help~

[Raymott]

I pronounce this couple to be husband and wife. You may kiss.

In this sentence, there is no article and it is not "a husband and wife." Some books say without article, "husband and wife" is a abstract concept. Does the sentence mean "I pronounce this couple having the husband-and-wife relationship"?

What's wrong if I use "pronounce them to be a husband and wife" ?

I appreciate your help~

It's just a collocation. To pronounce someone "a husband" simply means they have a wife. The marital couple are hoping to wed to each other.
It's similar to "These two people are father and daughter" This means that the man is the woman's father, and the woman is the man's daughter.
"These two people are a father and a daughter" doesn't have this meaning.
The man could be anyone's father and the woman anyone's daughter.

"husband and wife" has this meaning of mutual belonging.
You can say "Bill and Jane are husband and wife", and the implication is, "of each other".