حَدَّثَنَا عَفَّانُ حَدَّثَنَا مَسْعُودُ بْنُ سَعْدٍ حَدَّثَنَا خُصَيْفٌ عَنْ أَبِي عُبَيْدَةَ عَنْ أَبِيهِ قَالَ كَتَبَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي صَدَقَةِ الْبَقَرِ إِذَا بَلَغَ الْبَقَرُ ثَلَاثِينَ فَفِيهَا تَبِيعٌ مِنْ الْبَقَرِ جَذَعٌ أَوْ جَذَعَةٌ حَتَّى تَبْلُغَ أَرْبَعِينَ فَإِذَا بَلَغَتْ أَرْبَعِينَ فَفِيهَا بَقَرَةٌ مُسِنَّةٌ فَإِذَا كَثُرَتْ الْبَقَرُ فَفِي كُلِّ أَرْبَعِينَ مِنْ الْبَقَرِ بَقَرَةٌ مُسِنَّةٌ
مسند امام احمد بن حنبل · Hadith 3905
It was narrated from Abu 'Ubaidah that his father said: The Messenger of Allah (RA) wrote concerning zaknh on cattle: "When (the number of cattle) reaches thirty, a one year old, male or female, is due (as zaknh), up to forty. When (the number) reaches forty, a two year old, male or female, is due (as zakah). If the number of cattle is great, then for every forty, a two year old cow is due (as zakah)."
Sanad
حَدَّثَنَا عَفَّانُ حَدَّثَنَا مَسْعُودُ بْنُ سَعْدٍ حَدَّثَنَا خُصَيْفٌ عَنْ أَبِي عُبَيْدَةَ عَنْ أَبِيهِ