2 Peter 2:20-21:

For if after they have escaped the pollutions of the world through the knowledge of the Lord and Saviour Jesus Christ, they are again entangled therein, and overcome, the latter end is worse with them than the beginning.
For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them.

See also:

Objection: Healing Cannot Be in the Atonement Because Healing Can Be Lost, but Salvation Cannot Be Lost
Objection: We Don’t Have to Keep Getting Saved the Way We Have to Keep Getting Healed, So Healing Can’t Be in the Atonement