Kuajiri kunahusisha kutumia manufaa ya kitu kilichoajiriwa. Kwa upande wa mfanyakazi, kuajiri ni kutumia juhudi zake. Katika kumwajiri mfanyakazi, ni lazima kubainisha kazi, muda wa kazi, ujira na juhudi. Kazi lazima ibainishwe ili isibaki haijulikani, kwa kuwa kuajiri kwa kazi isiyojulikana ni batili (Fasid). Pia ni lazima kubainisha muda wa kazi, kama vile wa kila siku, wa kila mwezi au wa kila mwaka. Vivyo hivyo, ujira wa mfanyakazi lazima ubainishwe. Ibn Mas'oud alisema: Mtume ﷺ amesema: "Mmoja wenu akimwajiri mfanyakazi, basi amjulishe ujira wake." Pia ni lazima kubainisha juhudi ambayo mfanyakazi atalazimika kuitoa. Kwa hiyo, hairuhusiwi kumdai mfanyakazi kazi iliyo nje ya uwezo wake. Allah (SWT) amesema:

Hiring involves utilising the benefit of the hired thing. With regard to the worker, hiring is utilising his effort. It is necessary in hiring a worker, to define the work, the period of work, the wage and the effort. The work has to be defined so as not to become unknown, because hiring based on unknown work is invalid (Fasid). It is also necessary to define the period of work, such as daily, monthly or yearly. Similarly, the wage of the worker has to be defined. Ibn Mas’oud said: The Prophet (pbuh) (pbuh) said: “If any one of you employed a worker then He has to inform Him of his wage.” It is also necessary to define the effort that the worker has to expend. Accordingly it is not allowed to demand of the worker work that is beyond his capacity. Allah (swt) said:

“Allah haumlazimishi nafsi yoyote zaidi ya uwezo wake.” [Al-Baqarah: 286] Mtume ﷺ alisema: “Nikikuamrisha jambo, lifanyeni kadiri mnavyoweza”, kama alivyopokea Bukhari na Muslim kutoka kwa Abu Hurairah. Mfanyakazi asiombwe kufanya juhudi isipokuwa ile iliyo ndani ya uwezo wake wa kawaida. Kwa kuwa kipimo halisi hakiwezi kupima juhudi, kubainisha idadi ya saa za kazi kila siku ni kipimo bora zaidi kinachowezekana. Zaidi ya hayo, aina ya kazi nayo inapaswa kubainishwa, kama vile kuchimba udongo mgumu au laini, kufua chuma au kukata mawe. Hili pia huamua kiasi cha juhudi. Kazi hivyo itakuwa imebainishwa kwa kutaja aina yake, muda wake, ujira wake na juhudi iliyotumika ndani yake. Shari’a iliporuhusu kuajiri mfanyakazi, iliweka utaratibu wa kubainisha kazi yake kwa kuzingatia aina, muda, ujira na juhudi. Ujira anaopokea mfanyakazi, kama malipo ya utekelezaji wa kazi hiyo, ni mali aliyoipata kutokana na juhudi aliyoitumia.

“Allah burdens not a person beyond his scope.” [Al-Baqarah: 286] The Prophet (pbuh) (pbuh) said: “If I commanded you of something, do of it as much as you can”, as narrated by Bukhari and Muslim from Abu Hurairah. The worker should not be asked to undertake effort except that which is within his ordinary capacity. As a real scale cannot measure effort, defining the number of working hours every day is the best possible measure. In addition the type of work has to be defined as well, such as digging hard or soft soil, forging a metal or cutting stones. This also determines the amount of effort. The work would have thus been defined by stating its type, duration, wage and the effort spent in it.When Shar’a allowed employing a worker, it laid out provision for defining his work in terms of the type, duration, wage and effort. The wage received by the worker, in return for his execution of the work, is the property He accrued as a result of the effort He spent.