So when the [time of] promise came for the first of them, (17:5)

Almuntakhab Fi Tafsir Alquran Alkarim

When in due time the first occasion came to pass We humbled your arrogance by wedding you to a calamity. We sent against you servants of Ours invested with merciless power and martial daring who penetrated deep in the land and made their way right through your homes, and there the mission was accomplished and the promise fulfilled

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(17:5) When the occasion of the first of the two mischiefs came, O Israelites, We raised against you such of Our servants who were very mighty and formidable; so they penetrated through all parts of your country. This was a warning that was bound to be fulfilled. *7

So when the [time of] promise came for the first of them, meaning

*7) This refers to the terrible destruction that the Israelites suffered at the hands of the Assyrians and Babylonians. One cannot fully appreciate the historical background of this merely from the extracts that have been reproduced above from the Books of the Prophets. A brief history of the Israelites is also needed so that a student may become acquainted with all the causes and circumstances on account of which AIIah removed this nation, that professed to believe in a revealed Book, from the leadership of mankind and turned it into a humiliated, condemned and backward community.
When, after the death of Prophet Moses, the Israelites entered Palestine it was inhabited by the Hittites, Amorites, Canaanites, Perizzittes, Hivites, Jebusites, the Philistines, etc. These communities had adopted the worst kind of idolatry, their supreme deity being Ayl whom they regarded as the father of gods and who was usually represented by the bull-images. His consort was called Asherah from whom had descended a whole line of gods and goddesses, about 70 in number. The most powerful god among them was Baal who was regarded as the god of rain and growth and the lord of the earth and heavens. In the northern regions his consort was called Anathoth and in Palestine Ashtaroth. These two were the goddesses of love and procreation. Besides them, there was a god of death, a god of disease and famine, and a goddess of health, and thus all the worldly powers and agencies stood divided among a large number of deities. The people had ascribed such dirty and base qualities and acts to these deities that even a worst offender against morality would shun being known by them. Obviously the people who have adopted such mean deities for worship and devotion cannot remain secure from the worst kind of moral degeneration and the modern excavations have shown this conclusively.
Child sacrifice was a common thing among them. Their places of worship had turned into brothels, where women were kept as religious prostitutes and illicit relations with them were regarded as a part of worship and devotion.
The Israelites had clearly been told in the instructions given in the Torah that they should destroy those communities and wrest the land of Palestine from them, and that they should avoid mixing up with those people and ward off their moral and ideological weaknesses:
But when the Israelites entered Palestine they set this guidance aside. They not only did not establish a united kingdom of their own but fell a prey to tribal parochialism. Each of their tribes was content to take a part of the captured land and become a separate and independent state. This disunity among them did not leave any of the tribes strong enough to purge its territory completely of the idolaters, and therefore they had to allow them to live side by side with them in the same land. Not only this, but there had remained in the conquered territories a cumber of small city states of these idolatrous communities which the Israelites had nor been able to subjugate. It is this very thing which has been complained against in the extract of the Psalms reproduced above in the beginning of E.N. 6.
The first consequence of intermixing with those communities, was that the Israelites also became idolatrous, and gradually began to adopt other moral evils also. This has been complained about in the Book of Judges as below: "And the children of Israel did evil, in the sight of the Lord, and served Baalim: And they forsook the Lord God of their fathers, which brought them out of the land of Egypt, and followed other gods, the gods of the people that were round about them, and bowed themselves unto them, and provoked the Lord to anger. And they forsook the Lord, and served Baal and Ashtaroth". (Judges, 2: 11-13.)
The second consequence suffered by the Israelites was that the communities whose city-states they had left unconquered and the Philistines whose land they had not at all touched set up a united front against them and drove them out of a major part of Palestine by incessant attacks, so much so that they deprived them of the Holy Ark of their Lord. At last, the Israelites felt the need of Establishing a united kingdom of their own under one ruler, and on their request Prophet Samuel appointed Saul as their king in 1020 B.C. (For details see vv. 246-48 and E.N.'s. 268-270 of AI-Baqarah.)
This united kingdom was ruled by three kings: Saul (1020 B.C. to 1004. B.C.), Prophet David (1004 to 965 B.C.) and Prophet Solomon (365 to 926 B.C.). These kings brought to completion the mission that had been left incomplete by the Israelites after the death of Prophet Moses. They annexed all the territories except the Phoenician state on the northern and the Philistine state on the southern coast, which, of course, became tributaries.
After the death of Prophet Solomon the Israelites again adopted the ways of the world and fought among themselves and split into two independent kingdoms, the kingdom of Israel in the northern Palestine and Jordan with Samaria ,as its capital, and the kingdom of Judah in the southern Palestine and Edom with Jerusalem as its capital. These kingdoms were strife-ridden from the very . beginning and this state of affairs persisted till the end.
The rulers and people of the kingdom of Israel were the first to be affected grievously by the ideological and moral weaknesses of the neighbouring communities. Specially after the marriage of its ruler, Ahab, with the idolatrous princess Jezebel of Zidon, idolatry and other evils began to spread unchecked among the Israelites under the official patronage. Prophets Elias and Elisha tried their very best to check this deluge but the Israelites who were rapidly degenerating, did not heed their warning. At last the wrath of AIIah overtook the kingdom of Israel in the shape of the Assyrians who started subjecting Palestine to incessant attacks from 900 B.C. downward. During this period, Prophet Amos (787-747 B.C.) and them Prophet Hosea(747-735 B.C.) rose and warned the Israelites again and again but the wretched, depraved people did not heed their warnings at all, and transgressed all limits. Prophet Amos was banished by the king of Israel from the realm of Samaria and warned not to preach his mission in the country Not very long after this the wrath of Allah burst upon the kingdom of Israel and its people. The Assyrian king Sargon took Samaria in 721 B.C.and put an end to this northern kingdom. Thousands of Israelites were put to the sword and 27 thousand of their leading men were driven out of their homeland and scattered in the eastern districts of the Assyrian empire and replaced by settlers from other parts of the empire. When the remaining Israelites intermixed with the settlers they also lost gradually their national and cultural identity.
The other kingdom of the Israelites, called the kingdom of Judah, which was set up in southern Palestine also began to adopt godless ways soon after the death of Prophet Solomon, though its moral degeneration took place at a slower pace than that of Israel. Therefore, it was allowed to exist for a longer period. Then, like the kingdom of Israel, it also began to be subjected to continual attacks, its cities ruined and its capital besieged, but this kingdom could not be wholly destroyed by the Assyrians; it only became a tributary. Afterwards, when inspite of the best reformatory efforts of Prophets lsaiah and Jeremiah the people of Judah did not give up idol-worship and other moral evils, king Nebuchadnezzar of Babylon attacked and captured the whole of Judah in 598 B.C.including Jerusalem and took the king of Judah as prisoner. Even then the Israelites did not mend their ways and paid no heed to the warnings and guidance of Prophet Jeremiah: Instead of reforming their ways, they started making plans to change their fate by revolting against Babylon. At last in 587 B.C.Nebuchadnezzar punished them heavily by invading Judah and destroyed all its important cities. He razed Jerusalem and Solomon's Temple to the ground and did not leave a wall of it standing in place. He drove a large part of the Israelite population out of their land and scattered them into the adjoining countries. The people who were left behind were cursed and subjected to all kinds of humiliations by the neighbouring communities.
This was the first calamity that came as a warning to the Israelites and the first chastisement that they suffered as a result therof.
 

So when the [time of] promise came for the first of them, meaning in Urdu

آخرکار جب اُن میں سے پہلی سرکشی کا موقع پیش آیا، تو اے بنی اسرائیل، ہم نے تمہارے مقابلے پر اپنے ایسے بندے اٹھائے جو نہایت زور آور تھے اور وہ تمہارے ملک میں گھس کر ہر طرف پھیل گئے یہ ایک وعدہ تھا جسے پورا ہو کر ہی رہنا تھا