Sunan an-Nasai Book 41, Hadith 4229

أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا بِشْرٌ، - وَهُوَ ابْنُ الْمُفَضَّلِ - عَنْ خَالِدٍ، وَرُبَّمَا، قَالَ عَنْ أَبِي الْمَلِيحِ، وَرُبَّمَا، ذَكَرَ أَبَا قِلاَبَةَ عَنْ نُبَيْشَةَ، قَالَ نَادَى رَجُلٌ وَهُوَ بِمِنًى فَقَالَ يَا رَسُولَ اللَّهِ إِنَّا كُنَّا نَعْتِرُ عَتِيرَةً فِي الْجَاهِلِيَّةِ فِي رَجَبٍ فَمَا تَأْمُرُنَا يَا رَسُولَ اللَّهِ قَالَ ‏"‏ اذْبَحُوا فِي أَىِّ شَهْرٍ مَا كَانَ وَبَرُّوا اللَّهَ عَزَّ وَجَلَّ وَأَطْعِمُوا ‏"‏ ‏.‏ قَالَ إِنَّا كُنَّا نُفْرِعُ فَرَعًا فَمَا تَأْمُرُنَا قَالَ ‏"‏ فِي كُلِّ سَائِمَةٍ فَرَعٌ تَغْذُوهُ مَاشِيَتُكَ حَتَّى إِذَا اسْتَحْمَلَ ذَبَحْتَهُ وَتَصَدَّقْتَ بِلَحْمِهِ ‏"‏ ‏.‏

It was narrated that Nubaishah said:"A man called out while he was in Mina and said: 'O Messenger of Allah, we used to sacrifice the 'Atirah during the Jahiliyyah in Rajab; what do you command us to do?' He said: 'Sacrifice during whatever month it is, do good for the sake of Allah, the Mighty and Sublime, and feed (the poor).' They said: 'O Messenger of Allah, we used to sacrifice the Fara' during the Jahiliyyah; what do you command us to do?' He said: 'For every flock of grazing animals, feed the firstborn as you feed the rest of you flock until it reaches an age where it could be used carry loads, then sacrifice it, and give its meat in charity