1)    It is forbidden for a person to stand next to a field belonging to someone else and to look at it when it is standing with its crops “upright” (while the stalks are becoming ripe), so as not to damage it with the “evil eye”. It follows that it is even worse to look at a person in a way that it might possibly damage him with the “evil eye”. (Kitzur Shulchan Aruch 183)

2)    Even when a person is occupied with his business and other things in a way that there is no possibility of the “evil eye”, but he is doing this inside his own house, it is forbidden to look there without his knowledge as maybe he does not wish that others should know about his deeds and occupations. It is part of common etiquette that when a person sees someone else occupied with his work that he should bless him and say “You should be successful in your labors!”. (ibid)