He cites the divine decree as an argument when he commits sin, and says “Allah ghalib (Allah’s decree always prevails)”
Question

In our country, we often say “Allah ghalib (Allah’s decree always prevails)”, and that may be in the context of an excuse for not doing something. So for example, you might say to a person: Why did you not do such and such? And he will answer by saying: Allah ghalib. Or you may say: Why did you not keep your promise? And he will answer by saying: Allah ghalib. What is the ruling on saying this, especially in that context?
Praise be to Allah.Allah, may He be glorified and exalted, says (interpretation of the meaning):
{Allah’s decree always prevails, though most people do not realize} [Yusuf 12:21].
Ibn Kathir (may Allah have mercy on him) said:
That is, if Allah wants something to happen, it cannot be stopped, prevented or opposed; rather He is the One Whose decree always prevails over everything else.
Sa`id ibn Jubayr said: That is, He does whatever He wills. (End quote from Tafsir Ibn Kathir, 4/378).
Shaykh as-Sa`di (may Allah have mercy on him) said:
That is, His decree is always executed and nothing can cancel it out or oppose it, {though most people do not realize}. That is why they try to take measures to overcome the universal decree of Allah, but they are too weak and helpless to achieve that. (End quote from Tafsir as-Sa`di, p. 395)
This is like the verse in which Allah, may He be exalted, says: He is Dominant over His slaves} [al-An`am 6:18], and similar verses.
So if someone says “Allah ghalib (Allah’s decree always prevails)” intending to ascribe to Allah overwhelming power, might, glory and subjugation, then he has described Allah as He deserves.
But if his intention when saying that is to justify himself when falling short or committing sin, then he is misusing the concept of the divine decree as justification for that, because the divine decree can only be referred to when calamity befalls a person, and cannot be used to justify faults and shortcomings.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
It is obligatory to believe in the divine decree, but it is not permissible to use it as justification for going against the commands, prohibitions, promise and warning of Allah. (End quote from Majmu` al-Fatawa, 1/155)
He also said:
As using the divine decree as justification in such a manner is wrong according to people’s common sense and reason, no nation ever used it as justification (for sins and shortcomings). No interest could ever be achieved on the basis of this argument, in this world or the hereafter. (End quote from Majmu` al-Fatawa, 1/167)
Shaykh as-Sa`di (may Allah have mercy on him) said:
No wise person accepts the use of the divine decree as justification (for sins and shortcomings), even if he sometimes refers to it as justification for his situation, he would not persist in doing that. From an Islamic point of view, Allah has stated that using the divine decree as justification is wrong, and He did not mention that in the Quran except as something that was said by the polytheists who disbelieved in His messengers. (End quote from Tafsir as-Sa`di, 1/763)
Muslim (2664) narrated that Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “The strong believer is better and more beloved to Allah than the weak believer, although both are good. Strive to do that which will benefit you and seek the help of Allah, and do not feel helpless. If anything befalls you, do not say ‘If only I had done (such and such), then such and such would have happened,’ rather say: ‘It is the decree of Allah and what He wills, He does,’ for ‘if only’ opens the door to the work of the Shaytan.”
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Here the Prophet (blessings and peace of Allah be upon him) instructs the believer, when calamity befalls him, to connect his calamity to the divine decree and not dwell on the past; rather he should realize that what has befallen him could not have missed him, and what has missed him could not have befallen him. So he should think of the divine decree at the time of calamity and seek forgiveness from his shortcomings. (End quote from Majmu` al-Fatawa, 8/77)
He also said:
Man is not enjoined to think of the divine decree when he is enjoined to do what Allah has commanded him to do; rather he is enjoined to think of the divine decree when calamities befall him that he has no way to avoid. So whatever troubles befall you as a result of the actions of human beings or otherwise, you should show patience, accept it and surrender your affairs to Allah. (End quote from Majmu` al-Fatawa, 8/178)
It may be said to this person: As Allah’s decree always prevails, Allah, may He be exalted, is also a fair judge, and His is the creation and the command. He has commanded us to obey Him and has forbidden us to disobey Him, so referring to His decree and citing it as an excuse for going against His religion is the way of the polytheists, as Allah, may He be exalted, has told us, as He says:
{When they do something shameful, they say: We found our fathers doing this and Allah has enjoined it upon us. Say: Verily, Allah does not enjoin that which is shameful. Would you attribute to Allah something of which you have no knowledge?
Say [O Muhammad]: My Lord has enjoined the doing of what is right; direct your worship only to Him whenever you pray, and call upon Him with sincere devotion to Him alone. As He created you in the beginning, so you will be brought back [to life]}
[al-A`raf 7:28-29].
See also the answer to question no. 20806.
And Allah knows best.