1 Corinthians 3:1 calls them 'people of the flesh' — the factionalism in 3:4 is the proof of that carnality.

1 Corinthians 3:21 concludes the argument by forbidding boasting in human leaders — exactly the 'I follow Paul/Apollos' factionalism.

1 Corinthians 1:12 introduces the same factionalism — 'I follow Paul' and 'I follow Apollos' — that Paul here rebukes.

1 Corinthians 4:6 reveals that Paul uses himself and Apollos as object lessons to teach against the partisan spirit seen in 3:4.

2 Corinthians 12:20 lists quarreling and jealousy — the same fleshly behaviors that underpin the 'I follow Paul' divisions in 1 Cor 3:4.

Acts 19:1 places Apollos in Corinth historically, confirming the context of the partisan divisions Paul addresses.

Philippians 1:15 describes envy and rivalry in preaching — a similar spirit to the partisan boasting in 1 Cor 3:4.