(a) Abu Ubayd (may Allah have mercy on him) says: By his (peace and blessings be upon him) words "seven modes (ahruf)" are meant seven of the dialects of the Arabs; it does not mean that seven different vowelings are permissible in a single word. Such a view has never been heard from anyone. Rather, he says that these seven dialects are spread throughout the Qur'an: part of the Qur'an was revealed in the dialect of Quraysh, part in the dialect of Hawazin, some in the dialect of Hudhayl and some in the dialect of the people of Yemen; and likewise the other dialects. Their meanings are one and the same. This is made clear by the saying of Ibn Mas'ud (may Allah be pleased with him) mentioned above.
(b) Likewise, Ibn Sirin (may Allah have mercy on him) said that it is just like your saying: 'halumma, wa ta'al, wa aqbil' (come here, come, and approach). Then Ibn Sirin (may Allah have mercy on him) explained it, saying that in the reading of Ibn Mas'ud (may Allah be pleased with him) it is: "It was nothing but a single cry (zaqyah)," while in our reading it is "a single blast (sayhah)" [Surah Ya-Sin: 29], and the meaning of both is the same; and likewise the other dialects.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3992