1:14 shows Paul and the Corinthians mutually rejoice. This mutual joy is broken if Paul causes sorrow, as asked in 2:2.

2 Corinthians 7:8 reveals that Paul's sorrowful letter led to repentance. This resolves 2:2's worry by showing sorrow had good results.

11:29 shows Paul's empathy with the weak and offended. This deepens 2:2's question by revealing his personal investment in their feelings.

Romans 12:15 commands sharing in others' emotions. This principle underlies Paul's reasoning in 2:2 about mutual sorrow and joy.

1 Corinthians 12:26 describes the body's shared suffering and joy. This illustrates why Paul's making them sorry would affect his own joy.