Historical Rules · 5 October 2018
Rule 702.15e
Official source text from the 5 October 2018 Rules release
If multiple sources with lifelink deal damage at the same time, they cause separate life gain events (see rule 118.9). Example: A player controls Ajani’s Pridemate, which reads “Whenever you gain life, you may put a +1/+1 counter on Ajani’s Pridemate,” and two creatures with lifelink. The creatures with lifelink deal combat damage simultaneously. Ajani’s Pridemate’s ability triggers twice.