It takes one to know one.
Aithníonn ciaróg ciaróg eile.
Silence is golden.
Is binn béal ina thost.
Faraway hills are greener.
Is glas iad na cnoic i bhfad uainn.
A hint is enough for the wise.
Is leor nod don eolach.
Necessity is the mother of invention.
Múineann gá seift.