Symbol allows you to create a magical glyph that triggers on a condition you determine. One of the glyphs you can create is called Discord:
Each target must make a Constitution saving throw. On a failed save, a target bickers and argues with other creatures for 1 minute. During this time, it is incapable of meaningful communication and has disadvantage on attack rolls and ability checks.
Is a creature who fails the save against this effect capable of performing verbal spell components?