The ruling on one who takes one side of the Shari'ah and leaves the other side

Question:
One of the brothers says: There is no doubt that the Islamic Shari'ah came complete and comprehensive for all aspects of life. So what is the ruling on one who takes one side of the Shari'ah and neglects another side? This is the question.

Answer:
One who takes one side and neglects another side has taken what is right and neglected what is false. It is obligatory for him to adhere to the truth and to strive against his self in that, and not to take something and leave something. Then, there is a distinction in this: some of it results in disbelief (kufr) and some of it results in open sinfulness (fisq). Those who were upright in their worship and performed the acts of worship, such as prayer, fasting, zakah, and Hajj, and the like, but they fell into some of the forbidden things, such as unlawful sexual intercourse (zina)—may Allah protect us from that—or drinking intoxicants, or betrayal and deception in transactions, or the like of that, these are considered weak in faith, considered deficient in faith, and disobedient to their Lord, Mighty and Majestic. They do not become disbelievers, but rather they become open sinners, disobedient, weak in faith, and deficient in faith, if they do not consider these things permissible. As for one who considers them permissible and believes that zina is lawful, or that theft is lawful, or that betraying the Muslims is lawful, then for him is major shirk (associating partners with Allah), we seek refuge in Allah, after it is clarified to him so that the truth is made clear to him, if he is one who is ignorant of these matters. And likewise, one who rules by other than what Allah has revealed, if he considers that permissible, it becomes a departure from Islam and disbelief. And if he does this for a bribe or desire, and he knows that he is disobedient, and that he has contradicted the truth, but he left the Shari'ah ruling for desire or a bribe, or enmity between him and the one being judged, or for other reasons, then this is also misguidance, a deficiency in faith, a weakness in faith, and disbelief less than disbelief, as Ibn Abbas said. And this is among the details. As for one who commits disbelief with no doubt in it, then his acts of obedience do not benefit him; rather, his acts of obedience are invalidated, and he is judged by what he committed of disbelief. So if one prayed, fasted, gave charity, and the like, but he insults the religion, or insults Allah, or insults the Messenger, or lies about the Messenger of Allah and does not say that he is the Seal of the Prophets, or the like of that, then this is a disbeliever with major disbelief, and his deeds that he performs after that do not benefit him. So whoever commits any of the nullifiers of Islam, he is a disbeliever, and his acts of worship after that do not benefit him. So if he fasted during the day and stood in prayer at night and performed the obligations, but he says that Muhammad (peace and blessings be upon him) is not the Seal of the Prophets, he becomes a disbeliever. Or if he says that Usaym al-Jabbar is truthful and that he is a messenger with Muhammad, or that Yusuf ibn Abi 'Ubayd is truthful and that he is a messenger with Muhammad, all of this is a rejection of Islam. Or insulting the Messenger, or insulting Allah, or insulting the religion, or mocking the religion, he becomes a disbeliever with major disbelief. Or if he says that prayer is not obligatory, or that fasting is not obligatory, or that financial zakah is not obligatory, or that Hajj is not obligatory with the ability to perform it, this is a consensus among all the scholars, it is major disbelief, a departure from Islam. We seek refuge in Allah from the accursed Shaytan. So the conclusion is that one who takes one side and leaves a side of the religion, there is a distinction in it: you see that he may be a disbeliever, and you see that he may be a disobedient person weak in faith. We ask Allah for safety.