The Verse in Surah Yusuf:
And he said: 'O my sons! Do not enter by one gate, but enter by different gates, and I cannot avail you against Allah at all. Verily, the decision rests only with Allah. In Him, I put my trust and let all those that trust, put their trust in Him.' Al-Qur’an, 12:67
The majority of Mufassireen (authors of interpretation) are agreed that the brothers of Yusuf were handsome and good looking, and Yaqub (AS) feared that the people might affect them with the evil eye, for the evil eye is something real.
There is a verse in which Allah SWT says:
And verily, those who disbelieve would almost make you slip with their eyes (through hatred) when they hear the Reminder (the Qur'an), and they say: "Verily, he (Muhammad) is a madman!" But it is nothing else than a Reminder to all the 'Aalameen (mankind, jinn and all that exists). Al-Qur’an, 68:51-52
Ibn Abbaas, Mujaahid and others (RA) said: "Make you slip with their eyes" means, they will put the evil eye on you. This Verse is evidence that the effect and impact of the evil eye is something real and happens by Allah's will.
Ibn Katheer, 4/408