Reb Chaim Palagi (Refuah v'Chaim 12:74) writes, "When there is an ill person in one's home, he should practice וותרנות, to be generous, even with the birds of the sky, and they will certainly daven for him."
Chazal (Shabbos 32a) write, "A person should always daven that he shouldn't become ill, because if he becomes ill, heaven will tell him, 'Bring a merit and you will be cured.'"
Ben Ish Chai (Ben Yehoyada) asks, Why does Heaven tell him והפטר זכות הבא, 'Bring a merit and you will be cured'? Heaven knows if he has merits or not. Why must he 'bring a merit'?
Furthermore, if his merits didn't protect him from becoming ill, how will his merits help cure him?
The Ben Ish Chai replies that when Heaven says והפטר זכות הבא, "Bring a merit and you will be cured," this means that he should make a kabbalah tovah. That will be his merit to attain healing.
We quote the Ben Ish Chai:
"When someone is ill, a segulah to be cured from the illness is that he should accept a new mitzvah on himself. It should be something that he wasn’t doing previously, and it should be something that he isn't obligated to do הדין שורת פי על, according to the strict halachah. This is what the Gemara means when it says והפטר זכות הבא, bring a new merit, from the will of your heart, that you aren't obligated to do." This will be his merit that will heal him.
We add that the segulah will probably work also when other people in the family make a kabbalah tovah. This merit can heal the ill.
