The Messenger of Allah ﷺ as saying: Sacrifice only a full-grown animal unless it is difficult for you, in which case sacrifice a lamb.  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تَذْبَحُوا إِلاَّ مُسِنَّةً إِلاَّ أَنْ يَعْسُرَ عَلَيْكُمْ فَتَذْبَحُوا جَذَعَةً مِنَ الضَّأْنِ  

The Messenger of Allah ﷺ distributed sacrificial animals among his Companions. He gave me a kid (of less than a year). I took it to him and said: This is a kid. He said: Sacrifice it. so I sacrificed it.  

قَسَمَ رَسُولُ اللَّهِ ﷺ فِي أَصْحَابِهِ ضَحَايَا فَأَعْطَانِي عَتُودًا جَذَعًا قَالَ فَرَجَعْتُ بِهِ إِلَيْهِ فَقُلْتُ لَهُ إِنَّهُ جَذَعٌ قَالَ ضَحِّ بِهِ فَضَحَّيْتُ بِهِ  

On the authority of his father: We were with a man from the Companions of the Prophet ﷺ called Mujashi' who belonged to Banu Sulaim. There was a scarcity if goats (in those days). He commanded a man to announce (among the people); so he announced that the Messenger of Allah ﷺ used to say: A lamb may be given as full payent for that for which has full-grown animal is payment. Abu Dawud said: His name is Mujashi' b. Mas'ud.  

كُنَّا مَعَ رَجُلٍ مِنْ أَصْحَابِ النَّبِيِّ ﷺ يُقَالُ لَهُ مُجَاشِعٌ مِنْ بَنِي سُلَيْمٍ فَعَزَّتِ الْغَنَمُ فَأَمَرَ مُنَادِيًا فَنَادَى أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يَقُولُ إِنَّ الْجَذَعَ يُوَفِّي مِمَّا يُوَفِّي مِنْهُ الثَّنِيُّ  

The Messenger of Allah ﷺ delivered a sermon to us on the day of sacrifice after the prayer. He said: If anyone prays like our prayer, and sacrifices like our sacrifice, his sacrifice is all right. If anyone sacrifices before the prayer (for 'Id), that is goat meant for flesh. Abu Burdah b. Niyar stood up and said: Messenger of Allah, I swear by Allah, I sacrificed before I went for prayer. I thought it was the day of eating and drinking; so I made haste, and ate myself, and supplied flesh to my family and neighbors. The Messenger of Allah ﷺ said: That is a goat meant for eating flesh. He said: I have a kid (of less than a year) which is better than two goats meant for flesh. Will it be valid from me ? He said: Yes, but it will not be valid for anyone after you.  

خَطَبَنَا رَسُولُ اللَّهِ ﷺ يَوْمَ النَّحْرِ بَعْدَ الصَّلاَةِ فَقَالَ مَنْ صَلَّى صَلاَتَنَا وَنَسَكَ نُسُكَنَا فَقَدْ أَصَابَ النُّسُكَ وَمَنْ نَسَكَ قَبْلَ الصَّلاَةِ فَتِلْكَ شَاةُ لَحْمٍ فَقَامَ أَبُو بُرْدَةَ بْنُ نِيَارٍ فَقَالَ يَا رَسُولَ اللَّهِ وَاللَّهِ لَقَدْ نَسَكْتُ قَبْلَ أَنْ أَخْرُجَ إِلَى الصَّلاَةِ وَعَرَفْتُ أَنَّ الْيَوْمَ يَوْمُ أَكْلٍ وَشُرْبٍ فَتَعَجَّلْتُ فَأَكَلْتُ وَأَطْعَمْتُ أَهْلِي وَجِيرَانِي فَقَالَ رَسُولُ اللَّهِ ﷺ تِلْكَ شَاةُ لَحْمٍ فَقَالَ إِنَّ عِنْدِي عَنَاقًا جَذَعَةً وَهِيَ خَيْرٌ مِنْ شَاتَىْ لَحْمٍ فَهَلْ تُجْزِئُ عَنِّي قَالَ نَعَمْ وَلَنْ تُجْزِئَ عَنْ أَحَدٍ بَعْدَكَ  

A maternal uncle of mine called AbuBurdah sacrificed before the prayer (for 'Id). The Messenger of Allah ﷺ said: Your goat is meant for flesh. He said: Messenger of Allah, I have a domestic kid with me. He said: Sacrifice it, but it is not valid for any man other than you.  

لَهُ رَسُولُ اللَّهِ ﷺ شَاتُكَ شَاةُ لَحْمٍ فَقَالَ يَا رَسُولَ اللَّهِ إِنَّ عِنْدِي دَاجِنًا جَذَعَةً مِنَ الْمَعْزِ فَقَالَ اذْبَحْهَا وَلاَ تَصْلُحُ لِغَيْرِكَ