Ishāq bin Mansūr said:
Ahmad said: If he leaves the prayer, I will call him to repent for three days, according to the hadīth of Ibn ‘Umar (may Allah be pleased with him).
“Masā’il al Kawsaj” (3395)
Sālih said: I said: A man was neglectful regarding the prayer, then when death came, he acknowledged that (i.e. prayed)?
He (Ahmad) said: Prayer can’t be made up on his behalf, but you can give charity on his behalf.
I said: Verily he left it and did not pray?
He said: If he did it purposely, I would call him to repent for three days, so if he repented then fine, if not he is killed.
I said: So his repentance is that he prays?
He said: Yes.
“Masā’il Sālih” (295)