All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Whoever has sexual intercourse with his wife during the day of Ramadan has invalidated his fast, and he is obliged to repent, but he should continue fasting the rest of the day (though it would not count). He should also expiate for invalidating his fast; for more benefit on the expiation, please refer to Fatwa 83914.
As regards saying “Laa ilaaha illaallaah wahdahu laa shareeka lah, lahul-mulku walahul-hamd, wahuwa 'ala kulli shay'in qadeer” [None has the right to be worshipped except Allaah, Alone, without partners, to Him belongs all sovereignty and praise and He is over all things Omnipotent.], then according to the consensus of the scholars this does not wave the expiation. Had this been acceptable, the Prophet would have ordered people to resort to it, as he was most merciful for the believers.
The Prophet ordered the Bedouin who had sexual intercourse with his wife while he was fasting to free a slave, and if he is unable to do so, to fast for two consecutive months, and if he is again unable to do so, he should feed 60 poor persons. Had the above mention of Allaah been sufficient, then people would rush to transgress the Limits of Allaah and have sexual intercourse with their wives as it is very easy to expiate for their sin with the above mention of Allaah which one can say in less than 10 minutes; no person with a sound mind would accept this claim.