"I was killed by an old friend who grew tired of my company" by sprovo

After everything MIB went through to get Ben to stab Jacob, he screwed it up in the end.

Ben did stab Jacob and most likely would have been the cause of death. The problem is after the "they're coming" message from Jacob he kicks Jacob into the fire which is ultimately the cause of death. Ben's stab wound would have been the cause of death if MIB had waited a moment but since he didn't you can say Jacob could have been saved. Richard, Bram and Illana could have got to him and maybe saved him. The fact that they didn't have that opportunity means MIB caused the death not through manipulation but through kicking a wounded man into a fire.

Jacob confirms this in his quote to Hurley when he first reveals to Hurley he died an hour ago. He says "I was killed by an old friend who grew tired of my company". Now if MIB had waited a moment then Jacob would have said "I was killed by a man who was tricked by an old friend who grew tired of my company".

If anything this proves MIB is only human and capable of mistakes. Although age has brought him wisdom he still can make a simple mistake due to inexperience.