1. Determine your budget for your house purchase
2. Determine how much you will need for a down payment for said house purchase
3. Save aggressively for # 2

Ideally you are putting 20% down to avoid PMI. If you can’t, then the question becomes how large of a mortgage payment can you afford? The more you put as a down payment, the smaller your mortgage payment will be.

The most important thing about retirement savings is to get in the habit of setting money aside to give it time to grow. It’s difficult to determine if you should or should not contribute without knowing your expenses and the answers to the questions above.

I think of a house investment as another avenue for savings. You should certainly contribute enough to earn any matching funds from your employer.

Edit: There is a $10K exception to the early withdrawal penalty for your first home if you absolutely need the funds from an IRA but no exceptions for the 401K to avoid the 10% penalty in relation to a house purchase.