I have found 3 conditionals which have the word 'will' in the if clause! Are they correct?

Question

I have found in Syntax and Grammar of English Language by George Giannakopoulos the following:

If you will sign this agreement, I will let you have the money.

You can rarely use will in an if clause to show that somebody wants the other person to do something. In this case we use will to express somebody's willingness. In the sentence mentioned above we want to express the speaker's willingness. The speaker wants the other person to sign the agreement and let him have the money. Also we put a comma after an if clause when we start a sentence with the if clause.

I cannot create a link because the content of Syntax and Grammar of English Language by George Giannakopoulos is not available online.

I have found in Oxford English-Greek Learner's Dictionary by DN Stavropoulos & AS Hornby the following sentences:

1. If you will wait a moment I'll go and tell him that you are here.
2. Do you know if he will be at home tonight?
3. Let me know if you will come.

I believe that all the sentences mentioned above are wrong because they have the word will in the if clause! Also sentence 1 needs a comma after the if clause. This sentence should be written:

If you wait a moment, I will go and tell him that you are here.

Please have a careful look at them and tell me your opinions.

I cannot create a link because the content of Oxford English-Greek Learner's Dictionary by DN Stavropoulos & AS Hornby is not available online.

Answer 1

They are not wrong.

Will here has its older meaning of be willing to. It is actually a polite invitation: something like "Are you willing to sign this? If you do, then ... "

The Oxford example 3) is the same: it means "let me know if you are willing to/intend to come".

Example 2) is different: this is not a conditional, it is an embedded question. If could be replaced by whether.