Should I Return i797B & C to my employer after Stamping

My friend’s Stamping is done & now his employer is asking to return i797 B & C.

Should he return it to his employer OR keep it with him. What is the use of this form & what are the implications if he returns or keep it ?

Please help.

Lot of companies let you keep it. However, some paranoid employers would like to keep the documents with themselves as a mean to discourage you from changing employers.

If the employer is persistent in asking for the documents, just make copies for yourself and give it to them. You can still go for H-1 transfer using the copies.