It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that a man asked: O Messenger of Allah! Can a man pray in a single garment? He replied: "Does each of you find two garments, or does each of you have two garments?"
Hadith Referenceسنن دارمي / من كتاب الصللاة / 1408
In this hadith, the interrogative form is for negation, meaning: Does each of you not have two garments? If one has only a single garment, then he may perform prayer in that single garment.