Hadith 1963 - The Book of Sacrifices - Sahih Muslim - صحيح مسلم - Collection of Actions, Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم) - Kutub as-Sittah

35. The Book of Sacrifices - كتاب الأضاحى

2) Chapter: The age of sacrificial animals

Jabir reported Allah's Messenger (ﷺ) as saying:

Sacrifice only a grown-up animal, unless it is difficult for you, in which case sacrifice a ram (of even less than a year, but more than six months' age).

Reference: 1963
English reference: Book 22, Hadith 4836
In-book reference: Book 35, Hadith 19
Grade: Sahih
Read this hadith from Darussalam Collection

2) باب سِنِّ الأُضْحِيَةِ ‏‏

حَدَّثَنَا أَحْمَدُ بْنُ يُونُسَ، حَدَّثَنَا زُهَيْرٌ، حَدَّثَنَا أَبُو الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏‏ ‏.‏ "‏ لاَ تَذْبَحُوا إِلاَّ مُسِنَّةً إِلاَّ أَنْ يَعْسُرَ عَلَيْكُمْ فَتَذْبَحُوا جَذَعَةً مِنَ الضَّأْنِ ‏"