(a) Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) said: "Jibra'il (peace be upon him) taught me the Qur'an in one mode, and I kept going back to him and asking him to increase it, until he reached seven."
(b) Al-Zuhri (may Allah have mercy on him) says: These are seven modes; their ruling is one, and there is no difference among them regarding the lawful and the unlawful, that is, it is not the case that something is lawful in one mode and unlawful in another.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3990