Who is the Faithful and Wise Servant? It's a question that the WT has misused to establish its own authority. As it is, the parable today as a cautionary tale applies to whoever it fits, but it is clear who the original servant was that inspired the parable.
Genesis 39:4-5 says that "Joseph found favor in his lord's sight and was pleasing to him, and he appointed him over his house, and all that he had he gave into Joseph's hand. And it happened that after he appointed him over his house, and over all that was his, the Lord blessed the house of the Egyptian." Does that sound familiar in any way? The statement bears close resemblance with the Parable of the Faithful and Wise Servant (Luke 12:42-46) which begins with the question, "Who then is the faithful and wise servant whom the lord appointed over his house to give them rations of food at the appointed time?" The resemblance in wording is especially close when we examine the original Greek:
Luke 12:42 katestesen ... epi tes oiketeias autou "appointed over his house"LXX Gen. 39:4 katestesen auton epi tou oikou autou "appointed him over his house"
Genesis 39:4-5 is in fact the ONLY PLACE in the LXX where kathistemi is followed by epi + oik-. The closest other parallels are also from the story of Joseph (cf. Genesis 41:33, 40-43; 45:8; Psalm 105:21). Furthermore, the phrase became almost a stereotyped feature of the story of Joseph, related like a refrain in retellings of the story:
"The king ... appointed him lord over his house (katestesen auton kurion tou oikou autou)." (Psalm 105:21; LXX)
"Potiphar ... appointed (ashemo) Joseph over all of his house (diba kwellu betu)." (Jubilees 39:3)
"Joseph ... received authority over (epi) his fellow-servants and the charge of the whole household....[Potiphar] appointed (kathistato) him steward of his household (tes oikias)." (Philo, Joseph, 37-38)
"This chief officer of Pharaoh entrusted to me his household (ton oikon autou)." (Testament of Joseph 2:1)
"Potiphar ... committed the charge of his household (ton oikon) into his hands." (Josephus, Antiquities 2.39)
"Pharaoh ... appointed (katestesen) him ruler over Egypt and over all his household (eph' holon ton oikon autou)." (Acts 7:9-10)
"Pharaoh ... appointed (katestesen) me chief over (epi) the whole land of Egypt." (Joseph and Asenath 20:9)
Clearly Joseph was well remembered as the servant who had been appointed over the entire house of first Potiphar and then Pharaoh. What about the rest of Luke 12:42? There are four key words: "the lord" (ho kurios), "wise" (phronimos), "servant" (doulos), and "ration of grain" (to sitometrion) usually mistranslated as "food". Each of these terms has its counterpart in the traditions about Joseph. He is appointed by Potiphar, his "lord" (kurios, Genesis 39:3-4). He is especially "wise", as Genesis 41:33, 39 (LXX) applies phronimos to him, and in Psalm 105:21-22 (LXX) we read that Joseph taught wisdom (sophisai) to the elders of Eygpt. Joseph's wisdom was proverbial. Josephus (Antiquities 2.9 applies no fewer than six different synonyms (sophia, sunesis, dexiotes, phronesis, phronema, and logismos) to him, and Artapanus (fr. 2), Philo (Joseph, 117), Acts 7:10, Targum Onq. Genesis 37:3 all describe him as wise as well. Joseph is also his lord's "servant" (pais, Genesis 39:17, 19; 41:12), who had been sold into slavery. Although the LXX uses pais of Joseph, Philo and the Testament of Joseph use doulos to refer to him repeatedly (cf. Testament of Joseph 1:5, 11:2-3, 13:6-8, 15:2; Philo, Joseph 37, 47, 51, 66). And it is Joseph who supplies the rations of grain to Egypt during a time of famine after waiting through seven years of plenty (Genesis 41:53-57), clearly at the proper "appointed time".
Regarding this last point though the phrase to sitometrion "ration of grain" does not occur in the LXX, sitos "grain" is one of the key words in the story of Joseph, and the related verb sitometreo "deal out rations of grain" occurs only twice in the LXX -- and both with Joseph as the subject (Genesis 47:12, 14). Artapanus claimed that it was Joseph who discovered food rationing (metra; cf. fr. 2), and Luke's dounai/didonai + to sitometrion "give out rations of grain" recalls expressions throughout the Joseph literature that relate Joseph's deeds:
"your gift of grain (sitodosias)." (Genesis 42:19; cf. 42:33)
"Joseph ... ordered his steward to give them their measures of grain (siton ... dounai memetremenon).... Joseph still gave them grain (siton ... didontos)." (Josephus, Antiquities 2.189)
"He is giving grain (sitodotei) to the whole land....I too will go to my grain giving (sitodosian) and will give grain (doso siton)." (Joseph and Asenath 4:8; 26:3)
The parable in Luke 12:42-46 does not only share vocabulary with the story of Joseph. The situation of the faithful and wise servant is also similar to that of Joseph, not only in the theme of a servant becoming an overseer, but also in the motif of the lord being absent and delayed. According to Genesis 39:16, the lord's wife kept Joseph's garment "until his lord came (heos elthen ho kurios) home." This parallels Luke 12:43 which says: "Blessed is that slave who is doing so when his lord comes (elthon ho kurios autou)", and depicts the slave as present in the lord's home when the lord was absent. Jewish tradition explained that the lord was absent because everyone else had gone to a public festival (cf. Josephus, Ant. 2.45; b. Sotah 36b). Potiphar came home and found his slave not doing what he was supposed to be doing, and his wife told him: "This Hebrew was brought to us to berate us! He came in here to rape me, but I screamed" (Genesis 39:14). This recalls the faithless slave in the parable that figures that his lord "will be a long time in coming, and begins to beat the slaves, both men and women" (Luke 12:45). Luke 12:46-47 next mentions the lord's reaction: whipping the errant slave with "many lashes" and sending him "to the same fate as the unfaithful." This recalls the anger of Potiphar who then "took him and put him in prison" (Genesis 39:20). According to the Testament of Joseph (2:3; 13:9; 14:1-2), Joseph was "beaten" (tupto) -- the exact same verb used in Luke 12:45 to refer to the drunken servant beating the other slaves. An even closer parallel to the text of Luke can be found in the Testament of Joseph:
"If my lord was absent (apedemei), I drank no wine; for three-day periods I would take no food but give it to the poor and the ill. I would awaken early and pray to the Lord, weeping over the Egyptian women of Memphis because she annoyed me exceedingly and relentlessly." (Testament of Joseph 3:5-6)
Here what Joseph says is the exact opposite of the evil slave's actions: "If that slave says in his heart, 'My lord is delaying,' and begins to beat the slaves, both men and women, and to eat and drink and get drunk," and presumably fail to distribute the food rations he was appointed to do (Luke 12:45). In this text, Joseph declares himself to be faithful to his lord's wishes and presupposes that he sometimes carried out his lord's duties while his lord was away. This is precisely the situation in Luke 12:42-46, where we find the phrase elthon ho kurios which corresponds to the elthen ho kurios of Genesis 39:16 (LXX).
If there is any doubt regarding the dependence of Luke 12:42-46 upon the Joseph traditions, it is dismissed by Luke 12:44. Here we read of the lord's returning and finding his servant doing well. Jesus declares: "I tell you that he will appoint him over all his possessions." This is a variation of the original declaration, "Who then is the faithful and wise servant whom the lord appointed over his household to give them food rations on time?' We find exactly the same pattern in Genesis 39. After we twice read that the master appointed Joseph over his "house" (39:4-5a), the text continues: "The blessing of the Lord was upon all that he owned, in house or field." The blessing itself recalls Luke 12:43 which says "Blessed is that slave whom his lord finds doing so when he comes", but the LXX rendering of "all that he owned" (Heb. kl-'shr ysh-lw) lines up neatly with the Lukan text:
Luke 12:44 epi pasin tois huparkhousin autou LXX Gen. 39:5b en pasin tois huparkhousin autou
The phrase pasin tois huparkhousin occurs only one other place in the LXX, Judith 8:10, which unlike Luke 12:44 and Genesis 39:5 is not prefaced by a preposition, not followed by a masculine pronoun, and not preceded by the occurrences of kathistemi. The narrative in Judith 8 also bore little resemblance with the parable, unlike the story about Joseph and Potiphar's wife, and Joseph's exaltation under Pharaoh.
Thus we find that the Christian readers of Luke (and its Q predecessor), as followers of a "lord" promising to return, should find in Joseph a role model, particularly as one who was rewarded by Potiphar and later by Pharaoh for his faithful service. Interestingly, Acts 7:9-14 (also written by Luke) relates the story of Joseph and his exaltation as a theme of divine justice and vindication. The eschatological focus in the parable (e.g. referring to an end-time coming of the Lord) is also paralleled by Jewish tradition which focuses on Joseph's actions as prefiguring the Day of Judgment (cf. Jubilees 39:6; Targum Pseudo-Jonathan, Gen. 39:10; b. Yoma 35b). The Christian reader of Luke 12:42-46 would also think that the servant who says, "My lord is delayed," and then begins to beat others and eat and drink is the antithesis of the good and faithful Joseph; while the faithless servant eats and drinks and gets drunk, the extrabiblical traditions about Joseph go beyond Genesis in telling us that he fasted and refused to drink wine when his lord was away. Philo (Joseph, 45) also has Joseph telling Potiphar's wife that he will not be a "drunkard" (methuo). So it seems pretty clear that the "faithful and wise servant" in Luke intended to evoke the story of Joseph and his positive moral example.