The دعاء for protection from the evil eye is: 'A'udhu bikalimatillahit-tammati min kulli shaytanin wa hammah, wa min kulli 'aynin lammah' — I seek refuge in the perfect words of Allah from every devil and venomous creature, and from every evil eye. النبي used to seek this protection for Hasan and Husayn.
أُعِيذُكُمَا بِكَلِمَاتِ اللَّهِ التَّامَّةِ مِنْ كُلِّ شَيْطَانٍ وَهَامَّةٍ، وَمِنْ كُلِّ عَيْنٍ لَامَّةٍ
U'idhukuma bikalimatillahit-tammati min kulli shaytanin wa hammah, wa min kulli 'aynin lammah.
Meaning: I seek refuge for you both in the perfect words of Allah from every devil and venomous creature, and from every harmful evil eye.
Source: Sahih al-Bukhari #3371هذا الدعاء has a chain going back to Prophet Ibrahim (صلى الله عليه وسلم), who used it to protect Isma'il and Ishaq. النبي (صلى الله عليه وسلم) continued this practice with his own grandsons. The evil eye is real — النبي confirmed it saying: 'The evil eye is real, and if anything could outstrip the divine decree, the evil eye would outstrip it.' (صحيح مسلم 2188)
أُعِيذُكُمَا بِكَلِمَاتِ اللَّهِ التَّامَّةِ مِنْ كُلِّ شَيْطَانٍ وَهَامَّةٍ، وَمِنْ كُلِّ عَيْنٍ لَامَّةٍ
The Prophet (peace be upon him) used to seek protection for Hasan and Husayn, saying: 'U'idhukuma bikalimatillahit-tammati min kulli shaytanin wa hammah, wa min kulli 'aynin lammah.' And he would say: 'Your forefather Ibrahim used to seek protection with these words for Isma'il and Ishaq.'