Qatiloo allatheena la yu'minoona billahi wala bilyawmi al-akhiri wala yuharrimoona ma harrama (surah Tawbah: 29)

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

(9:29Fight with those from among the people of the Book, who do not believe in Allah nor in the Last Day; *26 who do not make unlawful that which Allah and His Messenger have made unlawful, *27 and do not adopt the Right way as their way. (Fight with themuntil they pay Jizyah with their own hands and are humbled. *28

Qaatilul lazeena laa yu`minoona billaahi wa laa bil yawmil Aakhiri wa laa yuharrimoona maa harramal laahu wa Rasooluhoo wa laa yadeenoona deenal haqqi minal lazeena ootul Kitaaba hattaa yu`tul jizyata ai yadinw wa hum saaghiroon

*26) Though the people of the Book professed to believe in Allah and the Hereafter, in fact they believed in neither. For only that person really believes in Allah who acknowledges Him as the only One God and the only One Lord, and does not associate with Him any other, whatsoever, in His Being, in His characteristics, in His rights and in His powers and authority. But according to this definition of shirk both the Christians and the Jews were guilty of shirk as has been made plain in the verses that follow: therefore their profession of belief in Allah was meaningless. Likewise they did not really believe in the Hereafter, in spite of the fact that they believed in Resurrection. For it is not enough: one must also believe that on that Day absolute justice will be done on the basis of one's belief and actions. One should also believe that no ransom and no expiation and no 'spiritual' relationships with any 'saint' shall be of any avail on that Day. It is absolutely meaningless to believe in the Hereafter without this. And the Jews and the Christians had polluted their faiths because they believed that such things would protect them against justice on that Day.
*27) The second reason why Jihad should be waged against them is drat they did not adopt the Law sent down by Allah through His Messenger.
*28) This is the aim of Jihad with the Jews and the Christians and it is not to force them to become Muslims and adopt the `Islamic Way of Life.' They should be forced to pay Jizyah in order to put an end to their independence and supremacy so that they should not remain rulers and sovereigns in the land. These powers should be wrested from them by the followers of the true Faith, who should assume the sovereignty and lead others towards the Right Way, while they should become their subjects and pay jizyah. jizyah is paid by those non-Muslims who live as Zimmis (proteges) in an Islamic State, in exchange for the security and protection granted to them by it. This is also symbolical of the fact that they themselves agree to live in it as its subjects. This is the significance of "..... they Pay jizyah with their own hands," that is, "with full consent so that they willingly become the subjects of the Believers, who perform the duty of the vicegerents of AIIah on the earth. "
At first this Command applied only to the Jews and the Christians. Then the Holy Prophet himself extended it to the Zoroastrians also. After his death, his Companions unanimously applied this rule to all the non-Muslim nations outside Arabia.
This is jizyah " of which the Muslims have been feeling apologetic during the last two centuries of their degeneration and there are still some people who continue to apologize for it. But the Way of Allah is straight and clear and does trot stand in need of any apology to the rebels against AIIah. Instead of offering apologies on behalf of Islam for the measure that guarantees security of life, property and faith to those who choose to live under its protection, the Muslims should feel proud of such a humane law as that of jizyah. For it is obvious that the maximum freedom that can be allowed to those who do not adopt the Way of AIIah but choose to tread the ways of error is that they should be tolerated to lead the life they like. That is why the Islamic State offers them protection, if they agree to live as its Zimmis by paying jizyah, but it cannot allow that they should remain supreme rulers in any place and establish wrong ways and impose them on others. As this state of things inevitably produces chaos and disorder, it is the duty of the true Muslims to exert their utmost to bring to an end their wicked rule and bring them under a righteous order.
As regards the question, "What do the non-Muslims get in return for Jizyah " it may suffice to say that it is the price of the freedom which the Islamic State allows them in following their erroneous ways, while living in the jurisdiction of Islam and enjoying its protection. The money thus collected is spent in maintaining the righteous administration that gives them the freedom and protects their rights. This also serves as a yearly reminder to them that they have been deprived of the honour of paying Zakat in the Way of Allah, and forced to pay jizyah instead as a price of following the ways of error.