What is the ruling on someone else speaking obscenities to me while I am fasting?

There is no sin upon you, nor any decrease in the reward of your fasting, if someone speaks obscenely in your presence while you are fasting; for the burden of sin is upon him alone, as Allah Almighty says: "And every soul earns not [sin] except against itself, and no bearer of burdens will bear the burden of another." Nevertheless, you should advise this person and caution him about the impermissibility of obscene speech.