When to set free house sparrow?

My cat attacked a house sparrow yesterday and we nursed it back to health, it's fine now. But I have to feed it very frequently! I don't know what to do, I can't do the job of a mother bird! She hasn't stopped chirping since I put her in the cage. Should I set her free? I really don't want to keep her as a pet, it's inhumane. Please answer quickly she wants me to feed her again!