Abdullah bin Masud reported,

The Prophet ﷺ said, "Let none of you, or any one of you, be prevented by Bilal's call from eating his pre-dawn meal, for he calls out, or announces, while it is still night so that the one praying among you may return to rest and the one sleeping may awaken. It is not that he is saying the dawn has come or the morning has arrived." He gestured with his fingers, raising them upward and lowering them downward, until he said, "Like this."Zuhayr, who is Ibn Muawiya al-Jufi, demonstrated with his two index fingers, one placed above the other, then extended them out to his right and to his left.

عن ابن مسعود

عن النبي ﷺ قال: لا يمنعن أحدكم- أو أحدا منكم- أذان بلال من سحوره، فإنه يؤذن- أو ينادي- بليل ليرجع قائمكم، ولينتبه نائمكم، وليس أن يقول: الفجر أو الصبح، وقال بأصابعه ورفعها إلى فوق، وطأطأ إلى أسفل- حتى يقول هكذا. وقال زهير ( وهو ابن معاوية الجعفي) بسبابتيه إحداهما فوق الأخرى، ثم مدها عن يمينه وشماله.