The following extract is taken from this
webpage. It is Herodotus discussing the roles and privileges of the Spartan kings. It was written about 430BC, so is a relatively reliable source, in that Herodotus probably had access to at least a few people with first-hand knowledge of the Spartan political system.
Bear in mind that spellings differ between alternate translations of ancient texts...
From The History of the Persian Wars, Book VI, ''56-60
These are the royal rights which have been given by the Spartans to their kings, namely, two priesthood---of Zeos Sparta and Zeos Uranios---and the right of making war against whatsoever land they please, and that no man of the Spartans shall hinder this right, or if he do, he shall be subject to the curse; and that when they go on expeditions the kings shall go out first and return last; that a hundred picked men shall be their guard upon expeditions; and that they shall use in their goings forth to war as many cattle as they desire, and take both the hides and the backs of all that are sacrificed. These are their privileges in war, and in peace moreover things have been assigned to them as follows: if any sacrifice is performed at the public charge, it is the privilege of the kings to sit down to the feast before all other, and that the attendants shall begin with them first, and serve to each of them a portion of everything double of that which is given to the other guests, and that they shall have the first pouring of libations and the hides of the animals slain in sacrifice; that on every new moon and seventh day of the month there shall be delivered at the public charge to each one of these a full-grown victim in the temple of Apollo, and a measure of barley-groats and a Spartan "quarter" of wine; and at all the games they shall have seats of honor specially set apart for them....
The kings alone give decision on the following cases only, that is to say, about the maiden who inherits her father's property, namely who ought to have her, if her father have not betrothed her to anyone, and about public ways; also if any man desires to adopt a son, he must do it in presence of the kings: and it is ordained that they shall sit in council with the elders, who are in number twenty-eight, and if they do not come, those of the elders who are most closely related to them shall have the privileges of the kings and give two votes besides their own, making three in all.
These rights have been assigned to the kings for their lifetime by the Spartan state; and after they are dead horsemen go round and announce that which has happened throughout the whole of the Spartan land, and in the city women go about and strike upon a copper kettle. Whenever this happens so, two free persons of each household must go into mourning, a man and a woman, and for those who fail to do this great penalties are prescribed.... a certain number of the perioiki are compelled to go to the funeral ceremony: and when there have been gathered together of these and of the helots and of the Spartans themselves many thousands in the same place, with their women intermingled, they beat their foreheads with a good will and make lamentation without stint, saying that this one who had died last of their kings has been killed in war, they prepare an image to represent him, laid upon a couch with fair coverings, and carry it out to be buried. Then after they have buried him, no assembly is held among them for ten days, nor is there any meeting for choice of magistrates, but they have mourning during these days.
When the king is dead and another is appointed king, this king who is newly coming in sets free any man of the Spartans who was a debtor to the king or to the state; while among the Persians the king who comes to the throne remits to all the cities the arrears of tribute which are due...
