人自愛其身, 惟有讀書, 人愛子弟, 惟有敎之讀書.
NOTES:[If] a person (人) loves himself (自愛其身), [he] only (惟) has (有) books to read (讀書). [If] a person (人) loves (愛) [his] children (子弟), [he] only (惟) has (有) books to teach them to read (敎之讀書).
As a pronominal adverb, 自 (자) means “self” or “personally,” and since it is an adverb, it always immediately precedes the verb, so 自愛 (자애) literally means “self (自) love (愛)” or “personally (自) love (愛). That means 自愛其身 (자애기신) literally means “personally (自) loves (愛) his (其) body (身),” which can be translated simply as “loves himself.” 讀書 (독서) can mean “read (讀) books (書),” so 惟讀書 (유독서) would mean “only (惟) read (讀) books (書),” but here there is the verb 有 (유), which means “to have,” suggesting there should be an object that follows it. That means 讀書 (독서) should be translated here as a noun phrase or clause. As a noun phrase, 讀 (독) would be treated as an adjective, in which case 讀書 would be translated as “reading (讀) books (書),” “books for reading,” or “books to read.” As a relative clause, 讀書 (독서) would translate as “books that are read” or “books that [one] reads.” Likewise, 敎之讀書 (교지독서) can mean “teach (敎) them (之) to read (讀) books (書),” but here it should be translated as “books to teach them to read” or “books that [one] teaches them to read.”
In Korean, the 讀書 (독서) here would be translated as “읽는 (讀) 책 (書),” and 敎之讀書 (교지독서) would be translated as “그들에게 읽기를 가르치는 (敎之讀) 책 (書).” 子弟 (자제) can mean “children,” “sons,” or “young people.”