«An old, thin man in a black tailcoat, short pantaloons, black silk stockings and shoes with buckles,» Herzen described Dr. Haas, a German doctor who came to Moscow to treat Russian princes at the beginning of the 19th century. As a result, he treated old people free of charge in almshouses, created a hospital «for the laborer class» and desperately tried to make life easier for exiles and convicts. Gaaz was not afraid to conflict with the authorities, with the prison administration. He managed to achieve the abolition of the iron rod, to which convicts were chained — six to eight people, completely different in age, build, height, health. It took more than a decade for the rod to be first replaced with a chain and then removed altogether. One of the main achievements of the German doctor is the relief of the weight of the shackle chains from 16 to 7 kg, so that they do not wash the legs into blood. Another important contribution of Gaaz to Russian history was his exploration of mineral springs.
Doctor Fyodor Petrovich Gaaz died on August 16, 1853. There was no property left after him. About 20 thousand people followed his coffin. He was buried at the Inoversky cemetery on the Vvedensky mountains — now this is the Lefortovo district in the east of Moscow. On the monument to Fyodor Petrovich Gaaz, as they began to call him in Russia, hang such shackles, which were lightened by him. And the inscription in Russian is visible: «Hurry to do good!»