The invention relates to a fitting for holding a probe, particularly a measuring probe or a sampling probe, with a housing, which has a space for holding the probe and a first chamber for holding a first fluid, which is connected to the space for holding the probe or comprises these, and which has a connecting section by means of which the housing can be connected or is connected to the container that serves to hold a medium whose property is to be measured by the probe or from which a sample is to be removed. At least one second chamber for holding a second fluid is provided inside the housing that is arranged between the first chamber and the connecting section of the housing. A measuring device is provided, by means of which at least one property of the second fluid in teh second chamber or flowing therefrom may be measured.