Congregate

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

Angel's Feather

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

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.)

Staff of the Sun Magus

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

Sunbond

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

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.

Swift Justice

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

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.

Lone Missionary

When Lone Missionary enters, you gain 4 life.

Dazzling Reflection

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

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.

Soulmender

Oreskos Sun Guide

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

Radiant Fountain

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

Soul's Attendant

Whenever another creature enters, you may gain 1 life.

Angel of Mercy

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

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.)

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.

Ajani's Mantra

At the beginning of your upkeep, you may gain 1 life.

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.

Elixir of Immortality

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

Profane Memento

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