Abu Dharr (May Allah be pleased with him) reported:
I asked: "O Messenger of Allah! Which action is the best?" He (ﷺ) said, "Faith in Allah and Jihad in the way of Allah." I asked: "Which neck (slave) is best (for emancipation)?" He said, "That which is dearest of them in price and most valuable of them to its masters". I asked: "If I cannot afford (it)?" He said, "Then help a labourer or work for one who is disabled". I asked: "If I cannot do (it)?" He said, "You should restrain yourself from doing wrong to people, because it (serves as) charity which you bestow upon yourself".[Al-Bukhari and Muslim].
Arabic/English book reference: Book 1, Hadith 117