Isaiah 49:8 is the direct source Paul quotes: 'In a favorable time I listened to you...' providing the foundation for the urgent 'now'.

Hebrews 3:7 stresses 'today' as the moment to respond—directly parallels Paul's insistence that now is the day of salvation.

Hebrews 3:13 echoes the 'today' urgency — exhort one another daily while it is called Today, reinforcing the present moment of salvation.

Hebrews 4:7 also cites Psalm 95:7 with 'Today' — the same urgency to respond to God's call without delay.

Psalm 32:6 urges prayer 'in a time when You may be found' — the same concept of seizing the opportune moment for seeking God.

Psalm 69:13 prays 'in the acceptable time' for God's mercy and salvation — directly echoing the phrase Paul quotes from Isaiah.

Proverbs 27:1 warns against boasting about tomorrow — a wisdom parallel to seizing today's opportunity for salvation.

Isaiah 55:6 urges seeking the Lord while He may be found – the same urgent call to act now before it's too late.

Luke 13:25 warns the door will be shut after the master rises – a strong parallel to seizing now before the day of salvation ends.

Acts 17:32 has some saying 'we will hear you again' – postponing response, contrasting Paul's insistence on 'now is the day of salvation'.

Luke 19:42-44 laments Jerusalem missing the time of visitation—contrasts with Paul's exhortation that now is the day of salvation.

Acts 24:25 shows Felix delaying the decision — a contrast to the urgent 'now' of salvation Paul proclaims here.

Ecclesiastes 9:12 says man does not know his time — an unpredictable snare, reinforcing the urgency to respond to salvation now.

Matthew 5:25 warns to settle quickly with your accuser while on the way – a parallel urgency to act now to avoid judgment.

Luke 12:58 similarly urges settling on the way to court – another parallel of urgent action before it's too late.