Spare the Dying

Source: Player's Handbook

Necromancy Cantrip (Artificer, Cleric, Druid)

Casting Time: Action
Range: 15 feet
Components: V, S
Duration: Instantaneous

Choose a creature within range that has 0 Hit Points and isn’t dead. The creature becomes Stable.

Cantrip Upgrade. The range doubles when you reach levels 5 (30 feet), 11 (60 feet), and 17 (120 feet).