Muwatta Malik, Book 26, Hadith 1074 (In-Book)

Yahya related to me from Malik from Rabia ibn Abi Abd ar-Rahman that Muhammad ibn Ibrahim ibn al-Harith at-Taymi said, "I heard my father say that the aqiqa was desirable, even if it was only a sparrow."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ رَبِيعَةَ بْنِ أَبِي عَبْدِ الرَّحْمَنِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ بْنِ الْحَارِثِ التَّيْمِيِّ، أَنَّهُ قَالَ سَمِعْتُ أَبِي يَسْتَحِبُّ الْعَقِيقَةَ، وَلَوْ بِعُصْفُورٍ ‏.‏

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also referenced under: Book 26, Hadith 5 (USC-MSA)