Your husband would enter the amount of the RRSP contribution on his return, and mark it as a spousal contribution.
You must make sure that the following CRA conditions are met: After December of the year you turn 71 years old, you can contribute, up to your RRSP deduction limit, to a spousal RRSP or common-law partner RRSP, if your spouse or common-law partner is 71 or younger on December 31 of the year you make the contribution.