The fact that only 3000 people were slain indicates there was some criteria used to determine who would live and who would be slain.<p>We do not hear what that criteria was for those who were slain.<p>I assume each was questioned about the GoldenCalf and their attitude toward it with respect to the Lord.  Those who preferred the GoldenCalf were slain.   Those that repented were saved.<p>When we look to the DayOfPentecost in which the HolySpirit was poured out, we see 3000 people turned to the LordJesusChrist and being saved.<p>The criteria for being saved is to receive Christ Jesus as MightyGod, Lord and Saviour.<p>It is worth noting that the unbelieving Jewish leadership persecuted Peter and the other disciples for their faith in Christ Jesus and their testimony of Him.<p>In the GoldenCalf episode everyone was saved but 3000.   On the DayOfPentecost everyone remained lost except the 3000.