In addition to the eight dusts, there are two other things that betray an impure mind of which we must be careful--these are falsehood and flattery. The words may be beautiful, but the mind is impure.

In the Ofudesaki are these words:

Tsukihi dislikes falsehood and flattery. If you persist, Tsukihi will withdraw.

Ofudesaki XII:113

Also, in the Osashizu, it is taught:

Even a single word of flattery is not needed. Flattery is a foundation of dirt.

Osashizu, April 20, 1898

Also:

You need not be reserved. Not saying as much as you would like out of deference will in the end become shackles. It will become a cloud over the Path.

Osashizu, June 14, 1901

You need not be reserved nor have too great a regard for other's feelings. For, these are the origin of dusts.

Osashizu, June 14, 1901

(The above is an excerpt from Dust and Innen, first published in September 1982. Quotations from the Ofudesaki and the Kakisage have been replaced by the revised, current translations.)