Glibness

Source: Player's Handbook

Level 8 Enchantment (Bard, Warlock)

Casting Time: Action
Range: Self
Components: V
Duration: 1 hour

Until the spell ends, when you make a Charisma check, you can replace the number you roll with a 15. Additionally, no matter what you say, magic that would determine if you are telling the truth indicates that you are being truthful.