The Messenger of Allah ﷺ said, "Let none of you be kept from his predawn meal by Bilal's call to prayer, for he calls out," or he said, "he gives the adhan, only so that the one of you who is praying may return and the one who is sleeping may be awakened. It is not that he says it like this," and Ibn Abu Adi Abu Umar brought his fingers together and pointed them downward, "but rather until he says it like this," and he spread apart his two index fingers, meaning the true dawn.
حدثنا ابن أبي عدي عن سليمان عن أبي عثمان
أن رسول الله ﷺ قال لا يمنعن أحدكم أذان بلال من سحوره فإنه إنما ينادي أو قال يؤذن ليرجع قائمكم وينبه نائمكم ليس أن يقول هكذا ولكن حتى يقول هكذا وضم ابن أبي عدي أبو عمرو أصابعه وصوبها وفتح ما بين أصبعيه السبابتين يعني الفجر