Allah says:

[أَوَلَمْ يَسيرُواْ]

(Have they not traveled), `these people who disbelieve in your Message, O Muhammad,'

[فِى الاٌّرْضِ فَيَنظُرُواْ كَيْفَ كَانَ عَـقِبَةُ الَّذِينَ كَانُواْ مِن قَبْلِهِمْ]

(in the land and seen what was the end of those who were before them) means, the nations of the past who disbelieved in their Prophets (peace be upon them), for which the punishment came upon them even though they were stronger than Quraysh.

[وَءَاثَاراً فِى الاٌّرْضِ]

(and in the traces in the land.) means, they left behind traces in the earth, such as structures, buildings and dwellings which these people [i.e., the Quraysh] cannot match. This is like the Ayat:

[وَلَقَدْ مَكَّنَـهُمْ فِيمَآ إِن مَّكَّنَّـكُمْ فِيهِ]

(And indeed We had firmly established them with that wherewith We have not established you!) (46:26)

[وَأَثَارُواْ الاٌّرْضَ وَعَمَرُوهَآ أَكْثَرَ مِمَّا عَمَرُوهَا]

(and they tilled the earth and populated it in greater numbers than these have done) (30:9). Yet despite this great strength, Allah punished them for their sin, which was their disbelief in their Messengers.

[وَمَا كَانَ لَهُم مِّنَ اللَّهِ مِن وَاقٍ]

(And none had they to protect them from Allah.) means, they had no one who could protect them or ward off the punishment from them. Then Allah mentions the reason why He punished them, and the sins which they committed. Allah says:

[ذَلِكَ بِأَنَّهُمْ كَانَت تَّأْتِيهِمْ رُسُلُهُم بِالْبَيِّنَـتِ]

(That was because there came to them their Messengers with clear evidences) meaning with clear proof and definitive evidence.

[فَكَفَرُواْ]

(but they disbelieved.) means, despite all these signs, they disbelieved and rejected the Message.

[فَأَخَذَهُمُ اللَّهُ]

(So Allah seized them.) means, He destroyed them utterly, and a similar fate awaits the disbelievers.

[إِنَّهُ قَوِىٌّ شَدِيدُ الْعِقَابِ]

(Verily, He is All-Strong, Severe in punishment) means, He is possessed of great strength and might.

[شَدِيدُ الْعِقَابِ]

(Severe in punishment, ) means, His punishment is severe and agonizing; we seek refuge with Allah, may He be blessed and exalted, from that.

[وَلَقَدْ أَرْسَلْنَا مُوسَى بِـَايَـتِنَا وَسُلْطَانٍ مُّبِينٍ - إِلَى فِرْعَوْنَ وَهَـمَـنَ وَقَـشرُونَ فَقَالُواْ سَـحِرٌ كَـذَّابٌ - فَلَمَّا جَآءَهُمْ بِالْحَقِّ مِنْ عِندِنَا قَالُواْ اقْتُلُواْ أَبْنَآءَ الَّذِينَ ءَامَنُواْ مَعَهُ وَاسْتَحْيُواْ نِسَآءَهُمْ وَمَا كَـيْدُ الْكَـفِرِينَ إِلاَّ فِى ضَلَـلٍ - وَقَالَ فِرْعَوْنُ ذَرُونِى أَقْتُلْ مُوسَى وَلْيَدْعُ رَبَّهُ إِنِّى أَخَافُ أَن يُبَدِّلَ دِينَكُـمْ أَوْ أَن يُظْهِرَ فِى الاٌّرْضِ الْفَسَادَ - وَقَالَ مُوسَى إِنِّى عُذْتُ بِرَبِّى وَرَبِّكُـمْ مِّن كُلِّ مُتَكَبِّرٍ لاَّ يُؤْمِنُ بِيَوْمِ الْحِسَابِ ]

(23. And indeed We sent Musa with Our Ayat, and a manifest authority,) (24. To Fir`awn, Haman and Qarun, but they called (him): "A sorcerer, a liar!'') (25. Then, when he brought them the Truth from Us, they said: "Kill with him the sons of those who believe and let their women live;'' but the plots of disbelievers are nothing but in vain!) (26. Fir`awn said: "Leave me to kill Musa, and let him call his Lord! I fear that he may change your religion, or that he may cause mischief to appear in the land!'') (27. Musa said: "Verily, I seek refuge in my Lord and your Lord from every arrogant who believes not in the Day of Reckoning!'')