Mishkat al-Masabih 4 Prayer كتاب الصلاة 856

وَعَنْ جَابِرٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا تَذْبَحُوا إِلَّا مُسِنَّةً إِلَّا أَنْ يَعْسُرَ عَلَيْكُمْ فَتَذْبَحُوا جَذَعَةً مِنَ الضَّأْن» . رَوَاهُ مُسلم

Jabir reported God’s Messenger as saying, “Sacrifice only a full- grown animal unless it is difficult for you, in which case sacrifice a she-lamb.” Muslim transmitted it.