I know numbers play a significant part in understanding the book of Revelation, but can you explain what the importance is of '144'? Eg. 144,000 Jewish virgin saints, and 144 cubits as the length of the New Jerusalem
The meaning of the number 12 in Scripture is God’s perfect rule through human agency or government. We see that meaning reflected in 12 apostles and 12 tribes of Israel. Furthermore in Hebrew, to double a number implies added emphasis (i.e., 12x2=24) and to multiply a number indicates the highest emphasis (i.e., 12x12=144). We see this rule at work in places like Matthew 18:
Matt. 18:21 Then Peter came and said to Him, “Lord, how often shall my brother sin against me and I forgive him? Up to seven times?”
Matt. 18:22 Jesus said to him, “I do not say to you, up to seven times, but up to seventy times seven.
Peter suggested that forgiving seven times would be enough (7 is the number of completeness), but Jesus answered that God’s expectation is that we would forgive our brother 70 times 7, which was a multiplication indicating highest emphasis (i.e., limitless forgiveness).
So when we see 144, we know this is a multiple of 12 indicating the highest emphasis on God ruling through human agency. The 144,000 virgin men are chosen specifically by God and called by God as His agents of salvation. Likewise, the measurements of the New Jerusalem place the highest emphasis on God ruling through and over His people in the New Jerusalem. The symbolism communicates that the population of the New Jerusalem owe their existence to God’s perfect plan manifested through the work of men like the apostles and the sons of Jacob.
You may find the following short article helpful as well: What is the significance of numbers in the bible?