All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The scholars provided two famous different opinions regarding the ruling of a person who does not pray out of laziness or negligence:
First: He is accused of minor disbelief but is still Muslim. This is the opinion of the majority of scholars.
Second: He is accused of major disbelief but is not judged as an apostate, unless he is commanded to repent by the ruler or his deputy. This is an opinion of Ahmad ibn Hanbal which was adopted by his followers, as stated by Al-Mardawi in Al-Insaf and As-Saffareeni in Ghitha’ Al-Albab. According to another opinion of Ahmad such a person is an absolute disbeliever. This opinion was adopted by a group of scholars including Shaykh Al-Islam Ibn Taymiyyah and it is supported by the apparent meaning of the texts.
According to the scholars who regard such a person as being Muslim, he is a disobedient and dissolute person.
As for cursing one who does not pray, we do not know of any authentic Hadeeth regarding this. However, it is permissible to curse him in general. Shaykh Al-Islam Ibn Taymiyyah was asked whether it is obligatory to curse a Muslim who prays only the Jumu‘ah (Friday) prayer. He answered:
"Praise be to Allaah. Such a person deserves punishment by the consensus of Muslims. According to the majority of scholars, including Maalik, Ash-Shaafi‘i and Ahmad it is obligatory to command him to repent and if he does not, then he must be killed. Cursing one who does not pray in general is permissible. However, it is better to avoid cursing a specific person, since he may repent."
Allaah Knows best.