Is it permissible to advise a non-Muslim neighbor to say "Masha'Allah" (what God wills) to ward off the harm of the envious eye, and would this saying remove the evil of his eye despite his disbelief?

If an unbeliever is known to be envious, he should be taught to invoke blessings upon what he sees of favors, saying: "Mā shāʾ Allāh, lā quwwata illā billāh" (What Allah wills! There is no strength save in Allah) to ward off his evil from Muslims. It is hoped that this will be a means of repelling the evil of his eye. This is indicated by the fact that the owner of the two gardens, who was advised to recite this remembrance, was an unbeliever. Therefore, there is no impediment to teaching him this remembrance to reduce his evil.