Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.   Wa alaikum assalam wa rahmatullahi wa barakatuh. As to what follows: In response to your question, we say:   If the muezzin calls out the athaan for Fajr at the proper time then it is not permissible to eat or drink, even if the person has the food or drink in his hand. Allah said, “and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night)” [al-Baqarah: 187]. The Prophet (peace be upon him) said, “Do not let the athaan of Bilal prevent you from partaking suhur because he calls out the athaan at night, but watch out for the athaan of ibn Um Maktum” [al-Bukhari (1819)]. There was an addition in an authentic narration that the Prophet (peace be upon him) said, “He (i.e., ibn Um Maktum) would not pronounce the athaan unless he was told that the day had dawned" [al-Bukhari (615)], that is dawn has appeared and is clear.