The full wording of the oath, affirmation and pledge is given here.

The wording of the oath is:
I (your name) swear by Almighty God that on becoming a British citizen, I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth the Second, her heirs and successors, according to law.

The wording of the affirmation is:
I (your name) do solemnly, sincerely and truly, declare and affirm that on becoming a British citizen, I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth the Second, her heirs and successors, according to law.

Citizenship pledge
You will also be asked to make a declaration, which is the citizenship pledge.

The wording of this declaration is the same whether you choose to swear an oath or affirm your allegiance.

The wording is:
I will give my loyalty to the United Kingdom and respect its rights and freedoms. I will uphold its democratic values. I will observe its laws faithfully and fulfil my duties and obligations as a British citizen.