You have my word
I am sorry. I don’t mean it. You have my word. I won’t do it again.
The work will be finished by the end of this week. You have my word!
I give you my word
I give you my word (that) I'll go.
A: Do you think you could do me a favor with this price?
B: Oh, of course......You know, normally we retail that for $29, but since you are such a good customer of ours, we will give you a discount. How's about 3% off? That's a higher discount than I give almost all of our customers.
A: Thanks! Does it come with insurance?
B: I'm sorry, I really wish I could do that for you, but our policy is to sell it without the insurance. If you would like to purchase that separately, I can give you a real deal on it.
A: That's okay. I'd like to look at some of the different models.
B: Oh! Yes. Take a look at this one. This is not usually available, we keep it behind the counter because it is limited edition. Of course, I know you're such a good friend, so I can let you have it at base rate.
A: Does it have a guarantee?
B: For you, I'll guarantee it personally! You have my word on it.