765/1 - Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Prophet (may Allah’s peace and blessings be upon him) prohibited blowing in one’s drink. A man said: “Sometimes I see a speck in the vessel. What should I do then?” He replied: “Spill it.” Then, the man said: “My thirst is not quenched with one gulp.” He said: “Then remove the cup from your mouth (in between three gulps, and take a breath).” [Narrated by Al-Tirmidhi; he classified it as Hasan Sahīh (sound and authentic)]
766/2 - Ibn ‘Abbās (may Allah be pleased with him and his father) reported: “The Prophet (may Allah’s peace and blessings be upon him) forbade breathing into the vessel or blowing in it.” [Al-Tirmidhi; he classified it as Hasan Sahīh (sound and authentic)]
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1) The Islamic Shariah is perfect in all aspects, even in the fine details concerning the etiquette of eating and drinking.
2) The forbiddance to blow into the vessel, lest harmful things come out. So, this instruction is aimed at protecting health and warding off harms. Is there a legislation more sublime than Islam?!