In Revelation 7, the number 144,000 is mentioned as being sealed from each of the twelve tribes of Israel. This number is also referenced in Revelation 14, where they are described as being redeemed from the earth and following the Lamb wherever he goes.
		
		
	 
In that same Revelation 14 context, the 144,000 is titled "the 
FIRST-fruits unto God and unto the Lamb".  This group of 144,000 Jewish saints shared the same title along with "Christ the
 FIRST-fruits" because these all shared the same bodily resurrection event in AD 33.  In other words, the 144,000 First-fruits coming from those Jewish tribes listed were the very same as 
the Matthew 27:52-53 saints who were raised from their broken-open graves around Jerusalem on the same day that Christ arose from the dead.   These 144,000 were OT Jewish saints coming from those various tribes who were bodily-raised to "live again" on that day.
For these 144,000 First-fruits to be "redeemed from the earth" meant that they were 
bodily resurrected out of the dust of the grave.  
For these 144,000 First-fruits to be called "virgins" is due to the fact that there is
 no marriage nor giving in marriage in the bodily-resurrected state.
For these 144,000 First-fruits to be described as "without fault before the throne of God" is something that can only be said of a bodily-resurrected saint. 
For these 144,000 First-fruits to "follow the Lamb wherever He goes" is the same as the Matthew 27:52-53 saints 
going into Jerusalem to be seen of many on the same day that
 the risen Christ was in Jerusalem on that first day of the week when He was showing Himself to His disciples.