When the opening verses of Surah Al-muzammil was revealed, the Companions would pray as long as they would pray during Ramadan until its last verses were revealed. The period between the revelation of its opening and the last verses was one year.
Reference: Sunan Abi Dawud 1305 In-book : Book 5, Hadith 56 English translation : Book 5, Hadith 1300
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