It is often very easy for practising muslims to judge and look down upon non practising muslims, forgetting quickly that it was only through the grace and mercy of Allah that they themselves were guided.
ْﻢُﻜْﻴَﻠَﻋ ُﻪّﻠﻟﺍ َّﻦَﻤَﻓ ُﻞْﺒَﻗ ﻦِّﻣ ﻢُﺘﻨُﻛ َﻚِﻟَﺬَﻛ
You, too, were once in the same condition – but God has been gracious unto you.
Narrated by Abu Hurayrah radiallahu anhu that he said, “I heared the Messenger of Allah Sallallahu alayhi wa sallam say:
“There used to be two brothers from the Children of Israel, one of them used to sin whilst the other was a strong worshipper. The worshipping brother never used to see the sinning brother except in the state of sin (always committing a sin). And he used to say to him “Decrease!” (in terms of how much sin he used to commit). Then one day he found him committing yet another sin whereupon he proclaimed “Decrease!”
So his brother said to him, leave me alone with my Lord (i.e only He can judge me), were you sent as a guardian over me?! So the worshipping brother said “By Allah! Allah will never forgive you! And you will never enter paradise!”
So their souls were taken (i.e they passed away) and were gathered in front of the Lord of the worlds. And (Allah) said to the worshipper “Did you have any knowledge of Me? Or did you possess the powers that I possesss?”
Then (Allah) said to the sinner “Go and enter Paradise by My Mercy” And (Allah) said to the other one “Take him away to the Hell fire!”
[Sunan Abu Dawood 4901]