The meaning of the sacrifice of Abraham's son.

Translation of Sahih Bukhari, Book 68: Al-Adha Festival Sacrifice (Adaahi) Volume 7, Book 68, Number 453: Narrated Al-Bara: The Prophet said (on the day of Idal-Adha), The first thing we will do on this day of ours, is to offer the ('Id) prayer and then return to slaughter the sacrifice. Whoever does so, he acted according to our Sunna (tradition), and whoever slaughtered (the sacrifice) before ...