The Messenger of Allah ﷺ said to Ali, "Ali, do not follow one glance with another, for the first is allowed to you, but the second is not."
قال رسول الله ﷺ لعلي: يا علي، لا تتبع النظرة النظرة، فإن لك الأولي، وليست لك الآخرة.
Reported by Abu Dawud (2148), Tirmidhi (2777), Hakim (2/194), Bayhaqi (90/7), Ahmad (22974), and Tahawi in Mushkil (1866), all of them through the hadith of Sharik, from Abu Rabia, from Ibn Burayda, from his father, and he related it.Sharik here is Ibn Abdullah Nakhai, who has poor memory, but he did not err in this particular hadith. The discussion of this is laid out in detail in the book on marriage.