1)
What is the significance of not taking a rock for the corner or the foundation?
1.
Radak: Normally, people take big rocks for the foundation, and for the corners of the walls. This is a metaphor, like the Targum - they will not take from you a king to rule, or an authority to rule.
2.
Malbim: People take valuable, solid rocks for the corner. This is a metaphor - they will not take from you a king. They will not take even rocks for the foundation, which are less [important] than cornerstones. I.e. even minor authority and settlement (they will not have).
