I remember often hearing this as a child. When other children would use things like wheelchairs or crutches, people would tell them not to, on the basis that it would be an "ayin hara" and might somehow cause them to eventually be injured and need said medical equipment. Is there any sort of source for this in Da'as Torah, or is this an "old wives' tale"?
Perhaps the source is Kesubos 68a:
ת"ר המסמא את עינו והמצבה את בטנו והמקפח את שוקו אינו נפטר מן העולם עד שיבא לידי כך המקבל צדקה ואין צריך לכך סופו אינו נפטר מן העולם עד שיבא לידי כך
The Gemara cites a baraita relating to swindlers who collect charity. The Sages taught: One who falsely blinds his eye, and one who bloats his stomach as if he were sick, and one who falsely crushes [mekape’aḥ] his leg, in order to benefit dishonestly from charity, will not depart from the world before he comes to this same plight, and he will truly suffer from the ailment that he feigned. More generally, one who receives charity and does not need it, his end will be that he will not depart from the world before he comes to this state of actually needing charity.