Tafsir Ibn Kathir -> Surah Az-Zumar -> It is an aspect of Man's Disbelief that He remembers Allah at times of difficulty then associates others with Him after He has been relieved of His Distress

﴿وَإِذَا مَسَّ الإِنسَـنَ ضُرٌّ دَعَا رَبَّهُ مُنِيباً إِلَيْهِ﴾

(And when some hurt touches man, he cries to his Lord, turning to Him in repentance.) means, at times of need, he prays to Allah and seeks His help alone, not associating anything with Him. This is like the Ayah:

﴿وَإِذَا مَسَّكُمُ الْضُّرُّ فِى الْبَحْرِ ضَلَّ مَن تَدْعُونَ إِلاَ إِيَّاهُ فَلَمَّا نَجَّـكُمْ إِلَى الْبَرِّ أَعْرَضْتُمْ وَكَانَ الإِنْسَـنُ كَفُورًا ﴾

(And when harm touches you upon the sea, those that you call upon vanish from you except Him. But when He brings you safe to land, you turn away. And man is ever ungrateful.) (17:67). Allah says:

﴿ثُمَّ إِذَا خَوَّلَهُ نِعْمَةً مِّنْهُ نَسِىَ مَا كَانَ يَدْعُو إِلَيْهِ مِن قَبْلُ﴾

(But when He bestows a favor upon him from Himself, he forgets that for which he cried for before,) means, at the time of ease, he forgets that supplication and prayer. This is like the Ayah:

﴿وَإِذَا مَسَّ الإِنسَـنَ الضُّرُّ دَعَانَا لِجَنبِهِ أَوْ قَاعِدًا أَوْ قَآئِمًا فَلَمَّا كَشَفْنَا عَنْهُ ضُرَّهُ مَرَّ كَأَن لَّمْ يَدْعُنَآ إِلَى ضُرٍّ مَّسَّهُ﴾

(And when harm touches man, he invokes Us, lying on his side, or sitting or standing. But when We have removed his harm from him, he passes on as if he had never invoked Us for a harm that touched him!) (10:12).

﴿وَجَعَلَ لِلَّهِ أَندَاداً لِّيُضِلَّ عَن سَبِيلِهِ﴾

(and he sets up rivals to Allah, in order to mislead others from His path.) means, at times of ease, he associates others in worship with Allah and sets up rivals to Him.

﴿قُلْ تَمَتَّعْ بِكُفْرِكَ قَلِيلاً إِنَّكَ مِنْ أَصْحَـبِ النَّارِ﴾

(Say: "Take pleasure in your disbelief for a while, surely, you are (one) of the dwellers of the Fire!'') means, say to those whose way this is, `enjoy your disbelief for a while!' This is a stern threat and solemn warning, as in the Ayat:

﴿قُلْ تَمَتَّعُواْ فَإِنَّ مَصِيرَكُمْ إِلَى النَّارِ﴾

(Say: "Enjoy! But certainly, your destination is the Fire!'') (14:30).

﴿نُمَتِّعُهُمْ قَلِيلاً ثُمَّ نَضْطَرُّهُمْ إِلَى عَذَابٍ غَلِيظٍ ﴾

(We let them enjoy for a little while, then in the end We shall oblige them to (enter) a great torment.) (31:24)

﴿أَمَّنْ هُوَ قَانِتٌ ءَانَآءَ الَّيْلِ سَـجِداً وَقَآئِماً يَحْذَرُ الاٌّخِرَةَ وَيَرْجُواْ رَحْمَةَ رَبِّهِ قُلْ هَلْ يَسْتَوِى الَّذِينَ يَعْلَمُونَ وَالَّذِينَ لاَ يَعْلَمُونَ إِنَّمَا يَتَذَكَّرُ أُوْلُو الاٌّلْبَـبِ ﴾

(9. Is one who is obedient to Allah, Ana'a Al-Layl prostrating and standing fearing the Hereafter and hoping for the mercy of his Lord Say: "Are those who know equal to those who know not'' It is only men of understanding who will remember.)