be for

be (all) for (someone or something)

To support or be in favor of a person, group, or effort. If management is considering adding a gym to the building, I'm all for it! I respect your opinion, but I'm for the other candidate. I don't know about the rest of you, but I'm all for going on a hike!
Farlex Dictionary of Idioms.

be for someone or something

 and be for doing something
supporting or in favor of someone or something. I'm for abandoning the scheme. Mary is running for office, and the whole family is for her.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

be for

v.
To be in favor of something or someone: I'm definitely not for cutting down the trees; we need the shade. Are you for these candidates, or against them?
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • be (all) for (someone or something)
  • be all for something/for doing something
  • be for it
  • go one-on-one with (someone)
  • gym shoe
  • masse
  • be a fine figure of a (man or woman)
  • en
  • en masse
  • be all very well
References in classic literature
But the fact is, that being, as I am, to inherit this estate after the death of your honoured father (who, however, may live many years longer), I could not satisfy myself without resolving to choose a wife from among his daughters, that the loss to them might be as little as possible, when the melancholy event takes place-- which, however, as I have already said, may not be for several years.
Pride and Prejudice
May I succeed, if to succeed be for my good and yours, or likely to avail me in my cause!
Apology
From our perspective, the only possible resolution of the matter at this time would be for the retained samples to be sent to an independent third-party laboratory for confirmatory analysis.
Missing link?: alachlor and semen quality