What does the verse command?
Radak, Malbim: Do not swindle via false measures and weights, like you did until now ? "Lehaktin Eifah u'Lehagdil Shekel u'Le'aves Mozenei Mirmah" (Amos 8:5).
Whom does the verse address?
Radak: It addresses the kings. The nation's sin is their sin, for they do not protest. Also, also they stole!
Malbim: The Nesi'im. It commands them to oversee that measures are just. This is included in doing Mishpat (verse 9). We appoint people to supervise this (Bava Basra 89a).
What is the scale used for?
Malbim: It is used to weigh coins 1 .
What is "Eifas"?
What is "u'Vas"?
Rashi: It is a measure of liquid.