Core Textטָעָה וְלֹא הִתְפַּלֵּל עַרְבִית — מִתְפַּלֵּל שַׁחֲרִית שְׁתַּיִם, דְּחַד יוֹמָא הוּא, דִּכְתִיב וַיְהִי עֶרֶב וַיְהִי בֹקֶר יוֹם אֶחָד.
If one erred and did not pray the evening prayer, he prays the morning prayer twice, because it is one day, as it is written “and there was evening and there was morning, one day.”