This entire episode can be better understood if we know: 
                              
                                - Why Joab told David not to follow  through with this idea of conducting a census.
 
                                - How Joab knew  David’s plan to have a census would “bring  guilt on Israel”? (Joab: “Why should  the king bring guilt on Israel?” – 1 Chron.21:3)
 
                               
                              At Mount Sinai in Exodus 30:11-15 God commanded Moses: 
                              
                                “When you take a census of the Israelites to count them, each one must  pay the Lord a ransom for his life at the time he is counted. Then no plague  will come on them when you number them. Each one who crosses over to those  already counted is to give a half shekel,  according to the sanctuary shekel, which weighs twenty gerahs. This half shekel is an offering to the Lord.  All who cross over, those twenty years old or more, are to give an offering to  the Lord. The rich are not to give more than a half shekel and the poor are not  to give less when you make the offering  to the Lord to atone for your lives.”  
                               
                              Joab did not want David to take the census because David was  merely counting the men for the king’s own purposes. When a leader like Moses took  the census as he did in Num. 1:1-2; 4:1-2;  
                                26:1-4, he did it at the Lord’s  command, “The Lord said to Moses and  Aaron: ‘Take a census…”  
                                But, for the king to take a census he is to collect  a half shekel “to atone for your lives” from each  
                                one “at the time he is counted.” When the Lord counts the people in a  census he is doing it for his purpose, but when the king takes a census he is  counting God’s people for the king’s business and because of this the people  must be atoned for with an offering given to the sanctuary.  
                              In David’s case there was no collection of the half shekel “to atone for your lives.” And, this is  because, there was no tabernacle or temple to bring the half shekel to as “an offering to the Lord.” 
                              First, Joab knew  David’s census was a bad idea because Joab knew there would be no half shekel collected  since there was no sanctuary to take it to. (The Lord had forbidden David the  chance to build one, 2 Samuel 7:4-17.) 
                              Second, Joab knew  this information from the Law of Moses recorded in Exodus 30:11-15. (David had  already made mistakes because he did not know the Law of Moses, such failing to  transport the Ark of the Covenant correctly, 2 Samuel 6:1-11). The Law of Moses  specifically says that, “When you take a  census of the Israelites to count them, each one must pay the Lord a ransom for  his life at the time he is counted. Then no plague will come on them when you  number them.” 
                              When the counting was finished David realized it was too late  for each Israelite to “pay the Lord a  ransom for his life at the time he is counted.” At this time David repents  and the prophet Gad shows up to ask David what form he would like to have his  plague: Famine, war, or plague? And, do you want it in three years, three  months, or three days?  |