Lifelink

[Spencer Addington]

My friend keeps insisting that lifelink only gives life equal to lethal damage to a creature and no more than it took to kill said creature.

Example: I attack with a 6/6 lifelink. He blocks with a 1/1. He says I only gain 1 life because the creature can't take more damage than is lethal. Is this true? I also need the exact ruling so he'll believe it.

[Spencer Addington]

I don't know he ruling, but you deal the full 6 damage to it.  That takes its toughness down to -5 and you gain 6.

I want to say I knew that, but his arguments were really convincing and it started to make me doubt. Thanks for confirming my original belief. Still need the official ruling though

[Keyeto]

Here's some rulings for you (give me a moment to get both):

702.15b: Damage dealt by a source with lifelink causes that source's controller, or its owner if it has no controller, to gain that much life (in addition to any other results that damage causes). See rule 119.3.

And here:

510.1c: A blocked creature assigns its combat damage to the creatures blocking it. If no creatures are currently blocking it (if, for example, they were destroyed or removed from combat), it assigns no combat damage. If exactly one creature is blocking it, it assigns all its combat damage to that creature. If two or more creatures are blocking it, it assigns its combat damage to those creatures according to the damage assignment order announced for it. This may allow the blocked creature to divide its combat damage. However, it can't assign combat damage to a creature that's blocking it unless, when combat damage assignments are complete, each creature that precedes that blocking creature in its order is assigned lethal damage. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures that's being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that's actually dealt. An amount of damage that's greater than a creature's lethal damage may be assigned to it.

Bolded for emphasis.

[Spencer Addington]

Here's some rulings for you (give me a moment to get both):

702.15b: Damage dealt by a source with lifelink causes that source's controller, or its owner if it has no controller, to gain that much life (in addition to any other results that damage causes). See rule 119.3.

And here:

510.1c: A blocked creature assigns its combat damage to the creatures blocking it. If no creatures are currently blocking it (if, for example, they were destroyed or removed from combat), it assigns no combat damage. If exactly one creature is blocking it, it assigns all its combat damage to that creature. If two or more creatures are blocking it, it assigns its combat damage to those creatures according to the damage assignment order announced for it. This may allow the blocked creature to divide its combat damage. However, it can't assign combat damage to a creature that's blocking it unless, when combat damage assignments are complete, each creature that precedes that blocking creature in its order is assigned lethal damage. When checking for assigned lethal damage, take into account damage already marked on the creature and damage from other creatures that's being assigned during the same combat damage step, but not any abilities or effects that might change the amount of damage that's actually dealt. An amount of damage that's greater than a creature's lethal damage may be assigned to it.

Bolded for emphasis.

THANK YOU! This is unbelievably helpful pal

[Pleeb]

that source's controller, or its owner if it has no controller

How would no one be controlling a creature? 

I can't think of any way a creature wouldn't have a controller, but like any good lawyer, wotc wrote it into the rules just in case.