12. A priest or deacon who married twice should not be ordained.

We learned, furthermore, that men of unexamined life, who even had many wives, boldly and freely aspire just as they please to the aforementioned ranks. We place blame for this not so much on those who reach for these things with immoderate ambition as on the metropolitan bishops specifically, who, when they close their eyes to forbidden strivings, disdain as far as is possible the precepts of our God. Let us be silent about what we suspect more deeply; but what of that which our God constituted in the law given through Moses, saying, "Let my priests marry once," [cf Lev 21:13] and in another place, "Let a priest take a virgin as a wife, not a widow, not a divorced woman, not a prostitute" [Ezek 44:22]?  Guided by this the Apostle, a persecutor turned preacher, commanded that both a priest and a deacon should be made "the husband of one wife." [1 Tim 3:2]  All of these things are thus despised by the bishops of your regions, as if they were decreed more in the opposite sense. And because we should not ignore presumptions of this sort, lest the just voice of an indignant Lord reproach us when he says, "You saw a thief and you ran with him, and you cast your lot with adulterers," [Ps 50(49):18] what henceforth should be followed by all churches, what should be avoided, we decree by general pronouncement.

 

[...]

 

15. Any cleric indeed who marries a widow or a second wife should thereupon be stripped of all privilege of ecclesiastical rank, with only lay communion conceded to him, which he can then have provided that he does nothing henceforth for which he should lose it.

 

(trans. R.  Somerville, B. Brasington; http://www.historyandapologetics.com/2015/02/letter-of-pope-siricius-to-bishop.html)