Wheel bearings don't last forever, and inevitably need replacing.
Saab 93's have a combined bearing and hub assembly, so replacement is - in principle - fairly straight forward, no bearing press required. The ABS sensor is also built into the assembly, so the procedure described here can also be used for replacing ABS sensors.
Although the procedure is quite straight-forward, if you're unlucky it can also be a bit of a pig. Although a hub puller shouldn't be required, it's advisable to have on one hand - unfortunately the driveshaft splines have a habit of rusting into the bearing, making it extremely difficult to remove the axle when required.
This documentation details signs of a failing front wheel bearing, as well as the process for replacing it on a >2003 Saab 93.