Spell Weapon (5e Feat)
From D&D Wiki
Prerequisites: The ability to cast at least one spell
During a short rest you can perform a 1 hour long ritual to imbue a weapon with your magic. The weapon must be within your reach for the entire duration. Doing this allows you to use that weapon as a focus for your spellcasting. If a damaging spell that is cast this way the weapon's damage type changes to the damage type of the spell for 1 minute due to lingering magic on the weapon. The magic fades when you complete a long rest.