If you do not aid the Prophet - Allah has already aided (9:40)

﴿إِلَّا تَنصُرُوهُ فَقَدْ نَصَرَهُ اللَّهُ إِذْ أَخْرَجَهُ الَّذِينَ كَفَرُوا ثَانِيَ اثْنَيْنِ إِذْ هُمَا فِي الْغَارِ إِذْ يَقُولُ لِصَاحِبِهِ لَا تَحْزَنْ إِنَّ اللَّهَ مَعَنَا ۖ فَأَنزَلَ اللَّهُ سَكِينَتَهُ عَلَيْهِ وَأَيَّدَهُ بِجُنُودٍ لَّمْ تَرَوْهَا وَجَعَلَ كَلِمَةَ الَّذِينَ كَفَرُوا السُّفْلَىٰ ۗ وَكَلِمَةُ اللَّهِ هِيَ الْعُلْيَا ۗ وَاللَّهُ عَزِيزٌ حَكِيمٌ﴾
[ التوبة: 40]

9:40 If you do not aid the Prophet - Allah has already aided him when those who disbelieved had driven him out [of Makkah] as one of two, when they were in the cave and he said to his companion, "Do not grieve; indeed Allah is with us." And Allah sent down his tranquillity upon him and supported him with angels you did not see and made the word of those who disbelieved the lowest, while the word of Allah - that is the highest. And Allah is Exalted in Might and Wise.

If you O believers, do not help the Messenger ( peace be upon him ) and respond to his call to strive for the sake of Allah, then Allah has already helped him when you were not with him; when the idolaters drove him away from Mecca with Abū Bakr aṣ-Ṣiddīq ( may Allah be pleased with him ), and the two of them hid in the cave of Thawr from the disbelievers who were chasing them.
On that occasion, the Messenger of Allah ( peace and blessings be upon him ) told his companion Abū Bakr, who was scared that the idolaters would discover him, not to worry, because Allah was with them, supporting and helping them.
Allah sent down His reassurance and tranquility upon the heart of His Messenger, and sent angels which they could not see to support them, making the word of the idolaters the lowest, and the word of Allah the highest by aiding His Religion.
Allah is Mighty in His essence, power and force – nothing can overcome Him – and He Wise in His planning, decree and laws.

If you help him (Muhammad SAW) not (it does not matter), for Allah did indeed help him when the disbelievers drove him out, the second of two, when they (Muhammad SAW and Abu Bakr) were in the cave, and he (SAW) said to his companion (Abu Bakr): "Be not sad (or afraid), surely Allah is with us." Then Allah sent down His Sakinah (calmness, tranquillity, peace, etc.) upon him, and strengthened him with forces (angels) which you saw not, and made the word of those who disbelieved the lowermost, while it was the Word of Allah that became the uppermost, and Allah is All-Mighty, All-Wise.

phonetic Transliteration

Illa tansuroohu faqad nasarahu Allahu ith akhrajahu allatheena kafaroo thaniya ithnayni ith huma fee alghari ith yaqoolu lisahibihi la tahzan inna Allaha maAAana faanzala Allahu sakeenatahu AAalayhi waayyadahu bijunoodin lam tarawha wajaAAala kalimata allatheena kafaroo alssufla wakalimatu Allahi hiya alAAulya waAllahu AAazeezun hakeemun

Abdullah Yusuf Ali - Translation

If ye help not (your leader), (it is no matter): for Allah did indeed help him, when the Unbelievers drove him out: he had no more than one companion; they two were in the cave, and he said to his companion, "Have no fear, for Allah is with us": then Allah sent down His peace upon him, and strengthened him with forces which ye saw not, and humbled to the depths the word of the Unbelievers. But the word of Allah is exalted to the heights: for Allah is Exalted in might, Wise.

Safi-ur-Rahman al-Mubarakpuri

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.

Page 193 English transliteration