Place it immediately after the promise is shown on screen, so it answers the claim directly. Follow it with a Bruh reaction when the promise falls apart, or cut to the Emotional Damage sound when the other person refuses to commit.
About this sound
This clip is a roughly 16-second Russian voice line in which a speaker firmly states that they need guarantees, delivering the phrase with a serious, demanding insistence that makes the request sound non-negotiable. It feels tense and stubbornly sceptical, like a refusal to take a promise at face value, and it works best as a blunt reaction when reassurance alone is not enough.