Wajawazna bibanee isra-eela albahra faataw AAala qawmin yaAAkufoona AAala asnamin lahum qaloo (surah Araf: 138)

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

(7:138) And We led the Children of Israel across the sea; and then they came upon a people who were devoted to the worship of their idols. They said: '0 Moses, make for us a god even as they have gods.' *98 Moses said: 'You are indeed an ignorant people.'

Wa jaawaznaa bi Banneee Israaa`eelal bahra fa ataw `alaa qawminy ya`kufoona `alaaa asnaamil lahum; qaaloo yaa Moosaj`al lanaa ilaahan kamaa lahum aalihah; qaala innakum qawmun tajhaloon

*98). The point at which the Israelites probably crossed the Red Sea lies somewhere between the present Suez and Ismailia. After that they headed towards the south of the Sinai peninsula along the coastal route. The western and northern regions of the Sinai peninsula were then included in the Egyptian empire. In the southern part of the peninsula, in the area lying between the present towns of Tur and Abu Zanimah, there were copper and turquoise mines. Since these were of immense value to the Egyptians, a number of garrisons had been set up to ensure their security'. One such garrison was located at a place known as Mafqah, which also housed a big temple. The ruins of this temple can still be found in the south-western part of the peninsula. In its vicinity there was an ancient temple, dedicated to the moon-god of the Semites. Passing by these places the people of Israel, who had been subservient to the Egyptians for a long time and were thus considerably Egyptianized in their outlook, felt the desire to indulge in idol-worship.
The extent to which the Israelites had become degenerated as a result of their slavery may be gauged by Joshua's last address to the Israelites delivered seventy years after their exodus from Epypt:
Now therefore fear the Lord, and serve him in sincerity and in faithfulness; put away the gods which your fathers served beyond the River, and in Egypt, and serve the Lord. And if you are unwilling to serve the Lord, choose this day whom you will serve; whether the gods which your fathers served in the region beyond the River, or the gods of the Amorites in whose land you dwell; but as for me and my house, we will serve the Lord (Joshua 24: 14-15).
This shows that even though the Israelites had been taught and trained by Moses for forty Years and by Joshua for twenty-eight years, they had still been unable to purge their minds of those influences which had warped their outlook and mentality during their period of bondage under Pharaoh. These Muslims had begun to look upon idol-worship as natural. Even after their exodus, the sight of a temple would incline them to indulge in the idolatrous practices which they had observed among their former masters.