Pledging from pension fund assets
You want to use pension fund assets as a security for the bank
While an early withdrawal will decrease your pension savings and thus your benefits, with a pledge no capital flows out of your retirement pension. You won't forgo any interest income, and your benefits won't change. Pledging merely serves as additional security for your bank. There would only be a reduction of your retirement savings capital with a corresponding loss of benefits if your bank should realize the pledge.
Information sheet on financing home ownership with pension fund assets