When you find another man with your wife
On the authority of Abu Hurairah that Sa'd bin 'ubaadah al-'anSaarii said: O Messenger of Allaah do you see it [befitting] that a man should kill another man who he finds with his wife.
The Messenger of Allaah (sallallaahu alayhi wa sallam) said: No.
Sa'd said: Yes, by the One who has honored you with the truth.
Thereupon the Messenger of Allaah (sallallaahu alayhi wa sallam) said: Listen [addressing a group of people] to that which your [addressing to plural group of people] Sayyid is saying.
عَنْ أَبِي هُرَيْرَةَ، أَنَّ سَعْدَ بْنَ عُبَادَةَ الأَنْصَارِيَّ، قَالَ يَا رَسُولَ اللَّهِ أَرَأَيْتَ الرَّجُلَ يَجِدُ مَعَ امْرَأَتِهِ رَجُلاً أَيَقْتُلُهُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ " . قَالَ سَعْدٌ بَلَى وَالَّذِي أَكْرَمَكَ بِالْحَقِّ . فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " اسْمَعُوا إِلَى مَا يَقُولُ سَيِّدُكُمْ
[Sahih Muslim 1498]
(بَلَى) أَيْ، بَلْ تَقْتَضِي الْغَيْرَةُ أَنْ يَقْتُلَ وَلَمْ يُرِدْ رَدَّ الْحُكْمِ فَإِنَّهُ بَعِيدٌ مِنْ مِثْلِ سَعْدٍ (اسْمَعُوا مَا يَقُولُ سَيِّدُكُمْ) أَيِ: انْظُرُوا إِلَى غَيْرَتِهِ حَيْثُ حَمَلَتْهُ عَلَى ذَلِكَ
(Yes) means that al-ghairah dictates that he kill and he was not refusing to accept the ruling of the Messenger of Allaah (sallallaahu alayhi wa sallam) as that is far fetched to believe when it comes to a person such as Sa'd.
(Listen to that which you Sayyid is saying) meaning look at his ghairah and to that which it is calling him [i.e. to say that one should kill].
Reference(s):
حاشية السندى على ابن ماجة