Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) states that the Prophet (peace and blessings be upon him) said to him: "O Ali, you have a treasure in Paradise, and you are the one with its two horns. So do not follow one glance with another, for the first is your right, but the second is not your right."
Ahmad recorded it; its chain contains Ibn Ishaq, who is a mudallis. The rest of its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 12944