Abdullah bin Amr bin As reported,
The Messenger of Allah ﷺ said, "Allah 
looks upon His creation on the night of the middle of Shaban and forgives His servants, except for two: one who harbors enmity and one who has killed a soul."
Ahmad 6642
Sahihحدثنا حسن حدثنا ابن لهيعة حدثنا حيي بن عبد الله عن أبي عبد الرحمن الحبلي
عن عبد الله بن عمرو
أن رسول الله ﷺ قال يطلع الله عز وجل إلى خلقه ليلة النصف من شعبان فيغفر لعباده إلا لاثنين مشاحن وقاتل نفس
No references are available.
Its isnad is sahih. It is found in Majma al-Zawaid 8:65, where it is said, Ahmad narrated it, and it contains Ibn Lahia, who is weak in hadith, but the rest of its narrators are trustworthy.Munziri mentioned it in Targheeb wa Tarheeb 2:80 and 3:283. In the first place he attributed it to Ahmad without noting any defect in it, while in the second place he said, Ahmad narrated it with a weak isnad.Abu Naeem also narrated its meaning in Hilyah 5:191, by way of Uzai, from Makhul, from Malik bin Yakhamir, from Muaz bin Jabal, as a raised report (marfu).