What is the ruling on a person who entirely neglects the prayer out of laziness and carelessness? Could you, please, highlight the opinions of all schools of Fiqh, especially the Hanbalis?

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 is His Slave and Messenger.

The vow of a person who neglects the prayer out of laziness and carelessness is valid and binding, and he is obliged to fulfill it because he is still considered a Muslim. However, if he denies the obligation of the prayer, then he is considered a disbeliever. According to the view of the majority of the scholars, denying the obligation of the prayer takes one out of the fold of Islam, as per the opinion held by Hanbali scholars; they considered the one who abandoned the prayer out of laziness to be out of the fold of Islam. Nevertheless, they also believe that the disbeliever's vow is valid and binding. Al-Hijjawi said, "A vow is valid and binding only if taken by an adult, sane person, even if he is a disbeliever." [Zad Al-Mustaqna‘]

Ash-Shawkani said:

"The scholars held different views regarding the vow of a disbeliever who converts to Islam and took a vow before his conversion. The preponderant opinion is that he is obliged to fulfill it, based on the Hadeeth of Ibn ‘Umar who reported that ‘Umar said to the Prophet, sallallaahu ‘alayhi wa sallam, "Oh Messenger of Allaah, I had taken a vow during the pre-Islamic period of ignorance (i.e. before embracing Islam) to observe I‘tikaaf (i.e. seclusion in the mosque for the purpose of worship) for one night in Al-Masjid Al-Haram." The Prophet, sallallaahu ‘alayhi wa sallam, said: "Fulfill your vow." [Nayl Al-Awtar]

Allaah Knows best.