Allah.

iftraḍa ʿalayhim: He made it obligatory for them.
aṭāʿūka li-dhālik: they believed in its obligation and carried it out.
iyyāka: a warning term.
wa-karāʾim: accusative of warning; plural of karīmah, the choicest and most valuable part of one’s wealth.
ittaqi daʿwata al-maẓlūm: beware the supplication of the oppressed; protect yourself from it by establishing justice and shunning wrongdoing.
fa-innahu: that is, “the matter is…”.
laysa baynahā wa-bayna Allah ḥijāb: there is no barrier between it and Allah; it is raised directly to Him and He accepts it.
akhrajāh: i.e., al-Bukhārī and Muslim both recorded it in their Ṣaḥīḥ collections.

General meaning of the ḥadith: When the Prophet ﷺ sent Muʿādh b. Jabal—may Allah be pleased with him—to Yemen as a preacher and teacher, he outlined for him the course he was to follow in his mission. He informed him that he would face knowledgeable and argumentative people from among the Jews and Christians, so he should be ready to debate them and refute their doubts. He was instructed to begin with the most important matter, then move to what comes next: first, to call the people to correct their creed, for it is the foundation; once they accepted that, he was to command them to establish the prayer, for after monotheism it is the greatest obligation. If they performed it, he was to instruct their wealthy to pay the zakāh of their property to their poor—out of solidarity with them and gratitude to Allah. He then warned him against taking the very best of their wealth, for what is due is the middle, average portion. Finally, he urged him to uphold justice and avoid oppression, lest the wronged person supplicate against him—and his supplication