Sunan an-Nasa'i, Volume 5, Book 41, Hadith 4236 (DarusSalam) ⓘ

It was narrated that Nubaishah said: "A man called out to the Prophet and said: 'We used to sacrifice the 'Atirah - i.e., during the Jahiliyyah - in Rajab; what do you command us to do?' He said: 'Sacrifice, whatever month it is, do good for the sake of Allah, the Mighty and Sublime, and feed (the poor).' He said: '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 your flock until it reaches an age where it could be used to carry loads, then sacrifice it, and give its meat in charity, for that is good."'

أَخْبَرَنَا أَبُو الأَشْعَثِ، أَحْمَدُ بْنُ الْمِقْدَامِ قَالَ حَدَّثَنَا يَزِيدُ، - وَهُوَ ابْنُ زُرَيْعٍ - قَالَ أَنْبَأَنَا خَالِدٌ، عَنْ أَبِي الْمَلِيحِ، عَنْ نُبَيْشَةَ، قَالَ نَادَى النَّبِيَّ صلى الله عليه وسلم رَجُلٌ فَقَالَ إِنَّا كُنَّا نَعْتِرُ عَتِيرَةً يَعْنِي فِي الْجَاهِلِيَّةِ فِي رَجَبٍ فَمَا تَأْمُرُنَا قَالَ ‏"‏ اذْبَحُوهَا فِي أَىِّ شَهْرٍ كَانَ وَبَرُّوا اللَّهَ عَزَّ وَجَلَّ وَأَطْعِمُوا ‏"‏ ‏.‏ قَالَ إِنَّا كُنَّا نُفْرِعُ فَرَعًا فِي الْجَاهِلِيَّةِ ‏.‏ قَالَ ‏"‏ فِي كُلِّ سَائِمَةٍ فَرَعٌ حَتَّى إِذَا اسْتَحْمَلَ ذَبَحْتَهُ وَتَصَدَّقْتَ بِلَحْمِهِ فَإِنَّ ذَلِكَ هُوَ خُيْرٌ ‏"‏ ‏.‏