Luke 21 opens with a small scene where Jesus notices a poor widow putting her last two coins in the offering at the temple, and it ends with Jesus' telling his disciples to be on guard as the end of days approaches, and the temple is destroyed
At only age 12, Jesus is already getting a picture of what his mission is here on earth. But instead of taking charge and building his army, he prepares for ministry by obeying Joseph and Mary.
When a stone mason begins building, he or she starts with one stone from which all the other stones are laid. As God is building believers into a spiritual house, there is one stone from which all the others derive purpose and significance.