RIGVEDA 1

अग्निमीळे पुरोहितं यज्ञस्य देवमृत्विजम् होतारं रत्न धातमम्
Translation:
The above mantra is benediction to Agni devta it states that verily the priest of the sacrifice and the sage and the fire god himself who invokes the deity let
sage and hothar of sacrifice praise Lord Agni with hymn one who is embodied with precious stones and radiant messenger of gods.
notes acharya sayana predicate that one should praise LordAgni who is priest of sacrifice who invocate the all god is embodied with precious stones so every sage or होतरा of sacrifice should praise God Agni with hymn and worship the god
Agni
commentary This is the first mantra of rigveda the worshipers ,the होतराcalled ऋत्विज has been stated all necessary predication has been explained in sacrifice all the relevant parts of the sacrifices necessarily predicated had been imposed on Lord Agni
पुरोहितं : The word " पुरोहितं " indicated to chief teacher or chief performer of‌ sacrifice so indicate necessarily that he should be Brahmin qualifed in Vedas or it indicate the अध्वुर्यु who is known to be ऋत्विज he is the Brahmin and he takes major role to perform ritual actions
necessarily the word पुरोहित can be predicated पुर: हितम् that means necessarily a Brahmin one who dually takes begining advantage is called पुरोहित because the word पुरा means begining हितम् means advantage so it can be predicated has a Brahmin one dually occupies the begining place and perform role of doing all major necessary actions in ritual is called पुरोहित
यज्ञस्य देवं : it means the direct god in sacrifice called has Lord Agni other dieties cannot be directly seen and also Lord agni is medium for major necessary anything offer made in fire so it can be predicated that all dieties notably indicated in Lord Agni so Agni place a major role in every sacrifice neither none can have major role in every sacrifice like that of Lord Agni
ऋत्विजं : The above word can be predicated has Brahmin himself usually in sacrifice there should be four ritvizas in them anybody can be chosen has purohit all ritvizas are qualified in Vedic rituals usually they choose knower of 4 vedas has purohit
होतारं The above word is predicted as hotru he is ritviza one who perform the role of inviting Vedic deites to sacrificial place same is predicated in next verses as स देवां एह वक्षति १:१:२ it means Agni is Lord does he actually invities dieties so it can be predicated the hotru is Brahmin actually he meant to invocate sacrificial fire
रत्न धातमम् The above word means that giver of every materialistic things to chief performer of sacrifice actually here the word ratna doesn't mean only precious stone it can be any materialistic things of well being it is given by Agni has consequent to sacrifice.