Code sharing

I have been working on a complex project for a while. I have successfully completed it. My manager has asked me to handover the code to one of my other colleague. He has been working on a different project for more than an year which didn’t go well. It seems he has complained that he is bored to work in the same project for an year . As a result, I have been asked to handover the finished product to him. Is this common in companies? I don’t understand what more development is in there apart from maintenance. I feel like it’s giving away the credits or sharing the credits for development.