[Tatzliach BeMaasecha].

Kitzur Shulchan Aruch, chapter 183, end of paragraph 5:

It is proper conduct [Derech Eretz] that when you see
your fellow occupied with his work, you should bless him
by saying:

May you succeed in your activities [Tatzliach BeMaasecha].

ALTERNATE TRANSLATION:
May you be successful with your work.

CHRONOLOGY:
Rabbi Shlomo Ganzfried lived in Hungary from 1804 to 1886 CE.
Kitzur Shulchan Aruch was first published in year 1864 CE.