Quran

This story indicates four clear traits of Thul-Qarnayn, first: He was a righteous and a just ruler. Second: He has an inspiration from Allah. Third: His kingdom was spread over large regions. Fourth: His conquests toward the west had reached an unknown place called: A hot spring of black muddy water. Ibn Ashur: 16/20.
Question: Allah may combine for a servant the blessings of this world and the Hereafter. Explain in light of this verse.

Allah does not detail what these means that He had given him were, and His Messenger (ﷺ) does not either. There are no reports that could give us any information regarding that. Therefore, we cannot but keep quiet about them. Al-Saadi: 485.
Question: What should be our attitude toward the things of which Allah and His Messenger (ﷺ) did not mention?

He used the means that Allah had given him in a proper manner. Not everyone who has means available to him uses those means, and not everyone is able to use the means available to him. If one has the true means of achieving something and uses them, his goal will be attained, but if both factors -or one of them- are absent, it will not happen. Al-Saadi: 485.
Question: When can one benefit from the means?

Meaning: Allah gave him power over them, and gave him choice. If he wanted to, he could kill the men, and take the women and children captive, or if he wanted to, he could set them free, with or without a ransom. His justice and faith became apparent in the ruling he pronounced. Ibn Kathir: 3/100.
Question: The believers are the most compassionate among people toward others. Explain in view of this verse.

Meaning: Paradise will be his, and he will be in good standing before Allah, as a reward on the Day of Resurrection. (And we will enjoin upon him to do what is easy), we will treat him kindly, speak gently to him, and be easy going with him. This indicates that Thul-Qarnayn was a righteous, knowledgeable and a just king, as he dealt with each person according to his situation, which is in accordance with what is pleasing to Allah. Al-Saadi: 485.
Question: What is the sign of success for a righteous ruler?

This verse proves that a ruler is obligated to protect his people, maintain their security, and fortify their borders using their public funds that they gain from outside sources, and what is available in their treasury. In case these public funds fall short, then they all have to compensate for it out of their own wealth. The ruler must manage these public funds wisely in accordance with these three conditions, first: He must not take exclusive possession of these funds. Second: He must start by helping the needy among them. Third: He must maintain equality among them in accordance with their eligibility. Al-Qurtubi: 13/384-385.
Question: Explain the duties of the Muslim ruler toward his people.

Meaning: Thul-Qarnayn told them: What Allah has given me of ability and sovereignty are much better than your reward and wealth. Al-Qurtubi: 13/384.
Question: Did Thul-Qarnayn become deluded by his sovereignty and ability, and forget Allah Who gave him all that?