Recast now or Refinance Later?

Hi, I bought a house this summer before selling my old house, so my mortgage has a large balance. Later in the summer, I sold my old house and the funds (a large amount) from that sale are sitting in my savings account.

Should I recast the mortgage now, applying the large amount of cash to my current mortgage (7.8%) or should I wait until the rate cut in september and refinance?