وَالشِّبْلُ فِي الْمَخْبَرِ مِثْلُ الْأَسَدِ
In tested ability, the lion-cub is like the lion.
Shibl is a lion-cub, and makhbar concerns inner qualities or qualities revealed by experience, not mere outward appearance. Abū Zayd uses the comparison to claim that his son shares his skill; it does not by itself justify the deception.