One of my English friends has written to me:
A teacher can receive no greater gift than to know he has had a positive influence on his students.
Here is my question: Why has he written to know with a to in front of know there? I myself think the sentence should instead be like this, without the to part:
A teacher can receive no greater gift than know he has had a positive influence on his students."
I think the use of to know there is wrong. Is it?