i don't have razavi's analog circuit book. if you scan it or give info about pg. 389 , may be i can say something more. And, tell me the topic of the chapter, oscillators or stability? give me more info pls.
when u focus on the ct u will find that there is 2 loops one for +ve FB and the other for -ve, So as there is +ve FB we have 2 make sure that this +ve FB will not make the ct oscillate so we need the -ve FB 2 more more that +ve FB by any factor
and i think that Razavi say by factor 2 for safety