Bismillah Arrahman Arraheem
As-salamu alaikum wa Rahmatullahi wa Barakatoh,
Holy Prophet Muhammad al Mustafā (salla llāhu ʿalayhi wa-alehe wa-sallam) said:
“One who fasts for four days in the month of Rajab, he will remain safe from calamities like the evils of Jinns, leprosy, leucoderma, mischief of Dajjal and the punishment of grave. He would get the reward of wise persons who repent. He would be handed over the scroll of deeds in his right hand and made to stand in the first row of worshippers"
[Reference: Sawaabul A’amaal Page 86]