Waking two week old to feed at night?

My son takes both formula and breastmilk (expressed due to problems in hospital). Do I wake him to feed at night or do I just wait for him to wake up and cry? He has been waking up every two/three hours or so anyways but there have been occasions where if I let him sleep it’ll be 3+ hours. Do I wake him to feed or just leave it until he’s ready??