"I came to the Prophet ﷺ and Bilal came out and called the Adhan and he started doing like this in his Adhan, turning to his right and left." (Using translation from Nasāʾī 643)  

أَتَيْتُ النَّبِيَّ ﷺ فَخَرَجَ بِلَالٌ فَأَذَّنَ فَجَعَلَ يَقُولُ «فِي أَذَانِهِ هَكَذَا يَنْحَرِفُ يَمِينًا وَشِمَالًا»