Allah admonishes those who lagged behind the Messenger of Allah in the battle of Tabuk, at a time when fruits were ripe and shades tempting in the intense and terrible heat,
﴿يَأَيُّهَا الَّذِينَ ءَامَنُواْ مَا لَكُمْ إِذَا قِيلَ لَكُمُ انفِرُواْ فِى سَبِيلِ اللَّهِ﴾
(O you who believe! What is the matter with you, that when you are asked to march forth in the cause of Allah), if you are called to perform Jihad in the cause of Allah,
﴿اثَّاقَلْتُمْ إِلَى الاٌّرْضِ﴾
(you cling heavily to the earth), reclining to remain in peace, shade and ripe fruits.
﴿أَرَضِيتُم بِالْحَيَوةِ الدُّنْيَا مِنَ الاٌّخِرَةِ﴾
(Are you pleased with the life of this world rather than the Hereafter), why do you do this, is it because you prefer this life instead of the Hereafter Allah next diminishes the eagerness for this worldly life and increases it for the Hereafter,
﴿فَمَا مَتَاعُ الْحَيَاةِ الدُّنْيَا فِى الاٌّخِرَةِ إِلاَّ قَلِيلٌ﴾
(But little is the enjoyment of the life of this world compared to the Hereafter.) Imam Ahmad recorded that Al-Mustawrid, a member of Bani Fihr, said that the Messenger of Allah said,
«مَا الدُّنْيَا فِي الْآخِرَةِ إِلَّا كَمَا يَجْعَلُ أَحَدُكُمْ إِصْبَعَهُ هَذِهِ فِي الْيَمِّ،فَلْيَنْظُرْ بِمَ تَرْجِعُ؟»
(The life of this world, compared to the Hereafter, is just like when one of you dips his finger in the sea, let him contemplate how much of it his finger would carry.) The Prophet pointed with his index finger. Muslim collected this Hadith. Ath-Thawri narrated that Al-A`mash said about the Ayah,
﴿فَمَا مَتَاعُ الْحَيَاةِ الدُّنْيَا فِى الاٌّخِرَةِ إِلاَّ قَلِيلٌ﴾
(But little is the enjoyment of the life of this world compared to the Hereafter.) "What compares to the provision a traveler takes.'' `Abdul-`Aziz bin Abi Hazim narrated that his father said, "When `Abdul-`Aziz bin Marwan was dying he said, `Bring the shroud I will be covered with so that I inspect it.' When it was placed before him, he looked at it and said, `Is this what I will end up with from this life' He then turned his back and cried, while saying, `Woe to you, O life! Your abundance is truly little, your little is short lived, we were deceived by you.''' Allah warns those who do not join Jihad,
﴿إِلاَّ تَنفِرُواْ يُعَذِّبْكُمْ عَذَابًا أَلِيمًا﴾
(If you march not forth, He will punish you with a painful torment) Ibn `Abbas said, "Allah's Messenger called some Arabs to mobilize, but they lagged behind and Allah witheld rain from coming down on them, and this was their torment.'' Allah said,
﴿وَيَسْتَبْدِلْ قَوْمًا غَيْرَكُمْ﴾
(and will replace you by another people), who will give aid to His Prophet and establish his religion. Allah said in another Ayah,
﴿الْفُقَرَآءُ وَإِن تَتَوَلَّوْاْ يَسْتَبْدِلْ قَوْماً غَيْرَكُمْ ثُمَّ لاَ يَكُونُواْ﴾
(And if you turn away (from the obedience to Allah), He will exchange you for some other people and they will not be your likes.) ﴿47:38﴾
﴿وَلاَ تَضُرُّوهُ شَيْئًا﴾
(and you cannot harm Him at all), you can never harm Allah when you lag behind and stay away from joining Jihad,
﴿وَاللَّهُ عَلَى كُلِّ شَيْءٍ قَدِيرٌ﴾
(and Allah is able to do all things.) He is able to destroy the enemies without your help.
﴿إِلاَّ تَنصُرُوهُ فَقَدْ نَصَرَهُ اللَّهُ إِذْ أَخْرَجَهُ الَّذِينَ كَفَرُواْ ثَانِيَ اثْنَيْنِ إِذْ هُمَا فِى الْغَارِ إِذْ يَقُولُ لِصَاحِبِهِ لاَ تَحْزَنْ إِنَّ اللَّهَ مَعَنَا فَأَنزَلَ اللَّهُ سَكِينَتَهُ عَلَيْهِ وَأَيَّدَهُ بِجُنُودٍ لَّمْ تَرَوْهَا وَجَعَلَ كَلِمَةَ الَّذِينَ كَفَرُواْ السُّفْلَى وَكَلِمَةُ اللَّهِ هِىَ الْعُلْيَا وَاللَّهُ عَزِيزٌ حَكِيمٌ ﴾
(40. If you help him (Muhammad ) not (it does not matter), for Allah did indeed help him when the disbelievers drove him out, the second of the two; when they were both in the cave, he said to his companion: "Be not sad (or afraid), surely, Allah is with us.'' Then Allah sent down His Sakinah (calmness, tranquillity, peace) upon him, and strengthened him with forces (angels) which you saw not, and made the word of those who disbelieved the lowermost, while the Word of Allah that became the uppermost; and Allah is All-Mighty, All-Wise.)