Bukhari

And Qadi Shurayh used to take a salary for judging, and Aisha (may Allah be pleased with her) said that the guardian (of an orphan) will take expenses according to his work, and Abu Bakr and Umar (may Allah be pleased with them both) also used to take a sufficient salary from the treasury (Bayt al-Mal) when they were caliphs.

Narrated 'Abdullah bin As-Sa'di: That when he went to 'Umar during his Caliphate. 'Umar said to him, "Haven't I been told that you do certain jobs for the people but when you are given payment you refuse to take it?" 'Abdullah added: I said, "Yes." 'Umar said, "Why do you do so?" I said, "I have horses and slaves and I am living in prosperity and I wish that my payment should be kept as a charitable gift for the Muslims." 'Umar said, "Do not do so, for I intended to do the same as you do. Allah's Apostles used to give me gifts and I used to say to him, 'Give it to a more needy one than me.' Once he gave me some money and I said, 'Give it to a more needy person than me,' whereupon the Prophet said, 'Take it and keep it in your possession and then give it in charity. Take what ever comes to you of this money if you are not keen to have it and not asking for it; otherwise (i.e., if it does not come to you) do not seek to have it yourself.' "

And Imam Hasan al-Basri (may Allah have mercy on him) said that Allah Almighty has taken a covenant from the rulers that they should not follow their desires and should not fear the people (Quranic verse) «ولا تشتروا بآياتي ثمنا قليلا‏» "And do not sell My verses for a small price." Then he recited this verse «يا داود إنا جعلناك خليفة في الأرض فاحكم بين الناس بالحق ولا تتبع الهوى فيضلك عن سبيل الله إن الذين يضلون عن سبيل الله لهم عذاب شديد بما نسوا يوم الحساب‏» "O Dawud! We have made you a successor on earth, so judge between the people in truth and do not follow desire, lest it lead you astray from the way of Allah. Surely, those who go astray from the way of Allah will have a severe punishment on account of their forgetting the Day of Reckoning." And Imam Hasan al-Basri recited this verse «إنا أنزلنا التوراة فيها هدى ونور يحكم بها النبيون الذين أسلموا للذين هادوا والربانيون والأحبار بما استحفظوا ، استودعوا ، من كتاب الله وكانوا عليه شهداء فلا تخشوا الناس واخشون ولا تشتروا بآياتي ثمنا قليلا ومن لم يحكم بما أنزل الله فأولئك هم الكافرون‏» "Indeed, We sent down the Torah, in which was guidance and light. The prophets who submitted [to Allah] judged by it for the Jews, as did the rabbis and scholars by that with which they were entrusted of the Scripture of Allah, and they were witnesses thereto. So do not fear the people but fear Me, and do not exchange My verses for a small price. And whoever does not judge by what Allah has revealed – then it is those who are the disbelievers." «بما استحفظوا ، استودعوا ، من كتاب الله» And Imam Hasan al-Basri also recited this verse from Surah Al-Anbiya «وداود وسليمان إذ يحكمان في الحرث إذ نفشت فيه غنم القوم وكنا لحكمهم شاهدين * ففهمناها سليمان وكلا آتينا حكما وعلما‏» "(And remember) Dawud and Sulayman, when they judged concerning the field when the sheep of a people overran it at night, and We were witness to their judgment. So We made Sulayman understand it, and to each [of them] We gave judgment and knowledge." Thus, Sulayman (peace be upon him) praised Allah and did not blame Dawud (peace be upon him). If the condition of these two prophets, whom Allah has mentioned, had not been as such, I would have thought that judges are perishing, because Allah Almighty praised Sulayman (peace be upon him) for his knowledge and excused Dawud (peace be upon him) for his ijtihad. And Muzahim bin Zafar said that Umar bin Abdul Aziz narrated to us that there are five qualities, and if a judge lacks any one of them, it is a defect for him. First, that he should have understanding of the religion; second, that he should be forbearing; third, that he should be chaste; fourth, that he should be strong; fifth, that he should be knowledgeable, and should acquire knowledge of religion from others as well.