What I expected to happen was by using the command /give @a[l=3,lm=3] minecraft:diamond (3 can be any number and it doesn't work with any item and it doesn't work with other arguments) it would give a level 3 player a diamond

What actually happened was
Nothing, it said it gave them a diamond but in actuality it didn't

Steps to Reproduce:
1. give yourself 3 levels
2. type /give @a [lm=3,l=3] (in chat or command block)
3. watch