What to say when you fear you may afflict someone or something with the evil eye
 

244. If you see anything of your brother that pleases you, or of his person or of his property [then ask Allah to bless him in it] for the envious eye is real, say:

اللّهُـمَّ بارِك عَلَـيه

ما شاءَ الله، لا قُوَّةَ إلاّ بالله

Allahumma baarik 'alayh

Ma shaa`allah laquwwata illa billah 

O Allah send blessings upon him

(This is) that which Allah has willed, there is no power except with Allah.

Reference: Ahmad 4/447, Ibn Majah, Malik. Al-Albani graded it authentic in Sahihul-Jami' As-Saghir 1/212. Also see Al-Arna'ut's checking of Ibn Al-Qayyim's Zadul-Ma'ad 4/170.