ما معنى "عدل رقبة من ولد إسماعيل" الوارد في الحديث؟

The hadith is authentic. "Equal to freeing a slave" means the equivalent reward, and "slave" refers to a bondsperson or a captive. The meaning of the hadith is that whoever recites the mentioned adhkar (remembrances) in the morning or evening will have a reward similar to that of freeing a slave from the progeny of Ishmael. This entails immense goodness and great reward, for whoever frees a slave, Allah will free each of their limbs from the Fire for each limb of the slave. The reason for specifically mentioning the progeny of Ishmael is that they were the most noble among those who were captured and enslaved.