Archangel of Thune

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
Whenever you gain life, put a +1/+1 counter on each creature you control.

Staff of the Sun Magus

Whenever you cast a white spell or a Plains you control enters, you gain 1 life.

Congregate

Target player gains 2 life for each creature on the battlefield.

Reviving Dose

Indestructibility

Enchant permanent
Enchanted permanent has indestructible. (Effects that say "destroy" don't destroy that permanent. A creature with indestructible can't be destroyed by damage.)

Angel's Feather

Whenever a player casts a white spell, you may gain 1 life.

Oreskos Sun Guide

Inspired — Whenever Oreskos Sun Guide becomes untapped, you gain 2 life.

Mass Calcify

Sunbond

Enchant creature
Enchanted creature has "Whenever you gain life, put that many +1/+1 counters on this creature."

Radiant Fountain

When Radiant Fountain enters, you gain 2 life.
{T}: Add {C}.

Dazzling Reflection

You gain life equal to target creature's power. The next time that creature would deal damage this turn, prevent that damage.

Soulmender

Profane Memento

Whenever a creature card is put into an opponent's graveyard from anywhere, you gain 1 life.

Ordeal of Heliod

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Heliod.
When you sacrifice Ordeal of Heliod, you gain 10 life.

Angel of Mercy

Flying
When Angel of Mercy enters, you gain 3 life.

Resolute Archangel

Flying
When Resolute Archangel enters, if your life total is less than your starting life total, it becomes equal to your starting life total.

Elixir of Immortality

{2}, {T}: You gain 5 life. Shuffle Elixir of Immortality and your graveyard into their owner's library.

Swift Justice

Until end of turn, target creature gets +1/+0 and gains first strike and lifelink.

Plains

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on Ajani's Pridemate.

Paragon of New Dawns

Other white creatures you control get +1/+1.
{W}, {T}: Another target white creature you control gains vigilance until end of turn. (Attacking doesn't cause it to tap.)

Angelic Accord

At the beginning of each end step, if you gained 4 or more life this turn, create a 4/4 white Angel creature token with flying.