The Messenger of Allah ﷺ forbade blowing or breathing into a vessel.  

نَهَى رَسُولُ اللَّهِ ﷺ أَنْ يُتَنَفَّسَ فِي الإِنَاءِ أَوْ يُنْفَخَ فِيهِ  

The Messenger of Allah ﷺ came to my father and he was a guest with him. He offered food to him and brought hais. He then brought a drink which he drank and he gave it to the one on his right. He ate dried dates and began to put the kernels on the back of his ring finger and middle finger. When he got up, my father also got up, and held the rein of his mount. He said : Pray to Allah for me. He said : O Allah, bless them in what you provided them, and have mercy on them.  

جَاءَ رَسُولُ اللَّهِ ﷺ إِلَى أَبِي فَنَزَلَ عَلَيْهِ فَقَدَّمَ إِلَيْهِ طَعَامًا فَذَكَرَ حَيْسًا أَتَاهُ بِهِ ثُمَّ أَتَاهُ بِشَرَابٍ فَشَرِبَ فَنَاوَلَ مَنْ عَلَى يَمِينِهِ وَأَكَلَ تَمْرًا فَجَعَلَ يُلْقِي النَّوَى عَلَى ظَهْرِ أُصْبَعَيْهِ السَّبَّابَةِ وَالْوُسْطَى فَلَمَّا قَامَ قَامَ أَبِي فَأَخَذَ بِلِجَامِ دَابَّتِهِ فَقَالَ ادْعُ اللَّهَ لِي فَقَالَ اللَّهُمَّ بَارِكْ لَهُمْ فِيمَا رَزَقْتَهُمْ وَاغْفِرْ لَهُمْ وَارْحَمْهُمْ