Issi b. Akiva says: Before the giving of the Torah, we were exhorted against the spilling of blood (of gentiles). After the giving of the Torah, instead of being more stringent, shall we be more lenient? In truth, they said: He (one who kills a gentile) is exempt from the laws of flesh and blood, but his judgment is relegated to Heaven. (Exodus, Ibid.) "to kill him with subtlety": to exclude a deaf-mute, an imbecile, and a minor, who are not "subtle."