Why? I believe your premise to be false. However, since you need something.......
In Acts 16:31-34 the Greek has
singular verbs, not
plural, to describe the action of believing. The text
does not say, the Jailer "and"
kai his household "believed"
plural. Thus, the notion that Luke nuanced the text to indicate the equal action of each member in believing, is incorrect and not provable linguistically. Instead, this text teaches what any OT believer might have expected: the Jailer, [the household head], "rejoiced
singular greatly, with all his house
panoikei, having believed
pepisteukos, participle,
singular) in God" (ASV). However, baptism was administered to each member of the Jailer's household: "he was baptized, he and all his household" [literally, those of his all]. Covenant membership has always included "you and your children" and covenant content is most fundamentally that the Lord is "God to you and your descendants" (Gen 17:7, Deut 7:9, 30:6, 1Ch 16:15, Psa 103:17, 105:8). (Notes from Gregg Strawbridge lectures). You can read
The Case for Covenantal Infant Baptism by Gregg Strawbridge or access some of his material at
Reformation Resources.
The notion that you put forth, that Luke gives us assurance of the salvation of the jailer, isn't found in the text, either.
God bless,
william
