A letter to the Daily Telegraph, signed by 61 people describing themselves as "leaders of Britain's major faiths", said the controversial legislation was being rushed through Parliament without proper debate.
Christian, Jewish, Muslim, Hindu and Buddhist figures were among those behind the appeal for a "pause".
The Marriage (Same Sex Couples) Bill arrives in the Lords on Monday for the start of what is expected to be a stormy passage through the upper chamber.
It survived a Commons backlash when 130 Tory backbenchers opposed the move.
Bishop Michael Hill, the Anglican Bishop of Bristol, Archbishop Bernard Longley, the Roman Catholic Archbishop of Birmingham and Bishop Angaelos of Britain's Coptic Orthodox Church, were among signatories.
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