Majma al-Zawaid — Hadith 11583

Sayyiduna Umar bin Abi Salamah (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said to Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him): "Indeed, the (other revealed) Books were sent down from heaven from a single gate, and the Qur'an has been sent down from seven gates in seven ahruf: the lawful, the unlawful, the clear (muhkam), the ambiguous (mutashabih), the striking of parables, command, and restraint (forbidding something). So treat as lawful what it makes lawful, regard as unlawful what it makes unlawful, act upon its clear verses, stop at its ambiguous verses, and take admonition from its parables, for all of it is from Allah Almighty, and none take heed except those of understanding."
Al-Tabarani recorded it; its chain contains a narrator, Ammar bin Matar, who is extremely da'if (weak), though some declared him thiqah (trustworthy).