Final answer:
The phrase 'a lamb to the slaughter' implies an innocent person is unknowingly heading into danger, and August's father probably uses it to indicate naivety about a situation.
Step-by-step explanation:
The phrase "a lamb to the slaughter" typically means someone is going into a situation in which they are unaware of the impending danger or harm. It originates from the idea that a lamb being led to be killed does not know what is coming and goes innocently and without resistance. August's father likely uses this phrase to express the sentiment that someone, possibly August, is heading into a situation naively or without recognizing the potential negative outcomes.