Sunnat at the time of sickness

Sayyida A’isha (Allah be pleased with her) narrates that whenever the
Messenger of Allah (Allah bless him & give him peace) would become ill,

he would recite the Mu’awwazathain (Surah al-Falaq & Surah an-Nas) and blow over
himself.

When his illness was aggravated, I used to recite these two Surahs
(and blow my breath) over him and make him rub his body with his own hand,
for its blessings.

(Sahih al-Bukhari, no. 4728)