《旧唐书·列传·卷六十七》
于是杀死了他的儿子，将用诚摔在地上，壮兵坐在他肚子上，用刀尖抵住他的喉咙说： 出声即死！ 
遂格杀其子，而仆用诚于地。壮士跨其腹，以刃拟其喉曰： 出声即死！ 
Then they killed his son, threw Yongcheng on the ground, the soldiers sat on his stomach, and held the tip of the knife against his throat and said: If you make a sound, you will die!
<s>[INST] Identify the key themes in this Classical Chinese text and explain them in English: 遂格杀其子，而仆用诚于地。壮士跨其腹，以刃拟其喉曰： 出声即死！  [/INST] Then they killed his son, threw Yongcheng on the ground, the soldiers sat on his stomach, and held the tip of the knife against his throat and said: If you make a sound, you will die!</s>
Identify the key themes in this Classical Chinese text and explain them in English: 遂格杀其子，而仆用诚于地。壮士跨其腹，以刃拟其喉曰： 出声即死！
user
Then they killed his son, threw Yongcheng on the ground, the soldiers sat on his stomach, and held the tip of the knife against his throat and said: If you make a sound, you will die!
assistant