The Messenger of Allah ﷺ said, "Every boy is held in pledge by his aqiqah, which is to be slaughtered for him on the seventh day, and his head is to be shaved and smeared with blood."Whenever Qatada was asked about the blood and how it should be applied, he would say, "When the aqiqah is slaughtered, take a piece of wool from it, hold it against the jugular veins, then place it on the soft spot of the baby's head so that the blood flows down upon his head like a thread. Afterwards his head is washed and shaved."
حدثنا حفص بن عمر النمري حدثنا همام حدثنا قتادة عن الحسن
عن رسول الله ﷺ قال كل غلام رهينة بعقيقته تذبح عنه يوم السابع ويحلق رأسه ويدمى فكان قتادة إذا سئل عن الدم كيف يصنع به قال إذا ذبحت العقيقة أخذت منها صوفة واستقبلت به أوداجها ثم توضع على يافوخ الصبي حتى يسيل على رأسه مثل الخيط ثم يغسل رأسه بعد ويحلق
Grading, [Its chain is daif]. See the following hadith. Tirmidhi transmitted it in the Book of Sacrifices, Chapter on the Sacrifice for the Newborn, no. 1522, and Nasai transmitted it, no. 4225, both from the hadith of Qatada with the same wording. Tirmidhi said, hasan sahih.His statement "it is smeared with blood" is anomalous, and its meaning is that the sheep is slaughtered on the child's behalf.Qatada narrated it using "an" without specifying direct hearing, and the following hadith suffices in its place. Allah knows best.