Allah's Messenger (ﷺ) used to pray two light rak`at before the morning (compulsory) prayer after the day dawned and the Mu'adh-dhin had finished his Adhan. He then would lie on his right side till the Mu'adh-dhin came to pronounce the Iqama.
Reference: Sahih al-Bukhari 626 In-book : Book 10, Hadith 23 USC-MSA web (English) : Vol. 1, Book 11, Hadith 599 (deprecated)
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