I found the answer, I'll post it to benefit all of you, here are the steps
1. Unexport the file system by entering:
exportfs -u /dirname
where dirname is the name of the file system you want to change, in this case /home3.
2. Open the /etc/exports file with your favorite text editor.
3. Make whatever changes you want.
4. Save and close the /etc/exports file.
5. Re-export the file system by entering:
exportfs /dirname
where dirname is the name of the file system you just changed in this case is /home3