How can I make a anti-jump script?

Just as the title says, im looking on a way how to make a script that wont allow the player to jump... Thank's in advance!

game.Players.PlayerAdded:connect(function(plr)
plr.Character.Humanoid:Changed:connect(prop)
if prop == "Jump" then
plr.Character.Humanoid.Jump = false
--plr.Character.Humanoid.Sit = false
end
end) 

What this script does is:

1. When a player enters the game, attach the function to it.
2. The function will detect whenever the player has jumped or Sitted. TODO: Don't let sitting also.
3. Change the Sit property to prohibit Jumping
4. ???
5. Profit