Narrated by Anas ibn Malik (Radi Allahu’Anhu): The Prophet Muhammad(ﷺ) said, “Who prays forty days sincerely for Allah in congregation catching the opening takbir, then two exemptions are written for him. He will be safe from the fire and free from hypocrisy.”
(Sunan at-Tirmidhi 241)
“Whoever prays for Allah”: This means sincerely for Allah’s, while seeking His pleasure.
“Forty days” : This is referring to the night prayer (Isha)
“Catching the opening takbir…”This means the Takbir Ihram with the Imam.
“Safe from the fire…” This means the person will be saved and rescued from Hell. Some scholars believe this refers to a person being safe from falling into debt and his shortcomings. Reason being, there is no way to be safe from Hell, except through repentance for both major and minor sins.
“Free from hypocrisy.” Entire Path
At-Taybi said: This implies that Allah protects him in this world from doing the actions of the Hypocrites. He will be granted the success to do the deeds done by the people of sincerity. In the Hereafter he will be saved from being punished like a hypocrite, or it will be witnessed that he isn’t a munafiq.
Verily, when hypocrites stand for prayer they stand lazy. The person in this hadeeth is nothing like them.