Need to clarify - used or new?
If your friend has a new package of lenses that suit you in all respects, then why not wear. And if you don't know if they are right for you, then you can check as a last resort.
But if you have never worn lenses before, this is not worth experimenting.
Lenses may not approach by optical power, and your eyes will quickly get tired or ache from the need to constantly strain.
The lenses may not fit in the curvature, and will try to jump out of the eye, or you will see a distorted picture.
The lens will also be unstable on the eye if its diameter or rigidity is not suitable for you.
In case of allergy to silicone, the silicone hydrogel lens may cause irritation.
If, however, we are talking about used lenses, then more serious troubles are possible. I agree with my colleague on the issue of hygiene. The ability to pick up other people's microbes is not a joke. Take care of your eyes!
Contact products are directly related to personal hygiene items. And you can't put it on yourself in the same way as you can not use your own toothbrush. It is difficult for a person to see the infection with the naked eye. With such actions, you can easily get eye irritation and infection by taking on the cornea a complex of microbial flora of the lens, which was used by another person.
If the lenses are intended not only to create a beautiful shade, but also to correct vision, this is doubly prohibited from doing. Since when visiting a doctor, he selects lenses for you according to your individual parameters, taking into account the optical power and lens material.
And if you have never worn lenses, you should consult an ophthalmologist. He will teach you the technique of putting on the lens, inform you about proper care and choose a pair of lenses that are absolutely safe for your eyes.
Be careful with such actions. Do not provoke the transmission of various eye diseases. Eye health comes first!