There are a few reasons it could matter. You didn’t provide enough info to tell for sure.
As long as you are a salaried/hourly employee and going to be performing the same line of work/job title or a promotion within that same line of work, you shouldn’t have any trouble. If a change occurs, it would be best to let your loan officer know when it will happen as most lenders will call your employer within days of closing to make sure you’re still employed. So keep them in the loop.
Things that would be a concern:
1. Changing careers
2. Changing jobs if you’re starting your own business
3. Changing jobs if the income used in qualifying is dependent on bonuses/commissions or overtime.