A lie is a false statement made by one to another one who is entitled to hear and to know the truth, and which false statement tends to work injury to the other.
Asilentone:
I believe the point being made is that if we fail to tell the truth to an individual who needs to know it, we could do him harm - work injury to him - by withholding information or by deliberately lying to him.
"To work injury" is simply an expression which may be peculiar to the WT. I'll have to check that out ...
Thanks,
CoCo