Rashi: The Navi commands them from Hashem, and Nochrim command them oppositely. The Navi returns and rebukes them, and they always say 'we have a command. Our command is more important than yours.'

Radak: Tzav is like Mitzvah. It is a noun. We do not find Tzav for a Mitzvah elsewhere. He commands them a little at a time, for they are like youths, whose hearts can accept only a little at a time.

Kli Paz: If Tzav l'Tzav (the one who commands, he himself fulfills the Mitzvos), he can command others to fulfill Mitzvos.

Malbim: He needs to command them what he already commanded them twice.

Rashi: They have a plumb-line - evil Mishpatim, corresponding to the line of Tzedek.

Radak: Kav is a builder's rod. He leans it until he makes a row [of bricks], and then removes it and leans it in order to make another row. He does so little by little until the wall is finished. So we teach and train children, and so the Navi must teach this nation, for they have little understanding, and are weary to hear Hashem's word, for they do not desire it. Tzav l'Tzav and Kav l'Kav are doubled, to strengthen the matter.

Kli Paz: If Kav l'Kav (if one makes a line for himself, so straighten his deeds), he is proper to straighten others.

Malbim: It is not enough to command them repeatedly. He must also draw lines, like one teaches children via lines and pictures. What he already taught via a line, he must draw a second line.

Rashi: The Navi tells them, in a little more time, evil will come upon you, and they say, let Him bring His deed soon!

Radak: [The Navi tells the nation] a little about this matter, and a little about this matter, and even so, they do not accept.

Kli Paz: If one has only a little perfection, he can command and straighten others only a little. He cannot command others to be better than himself!

Malbim: He cannot teach and draw many things at once, only a little at a time, in different matters, the way that one teaches children.