In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Question: What is the ruling regarding being in a state of Janaabah during the daytime in Ramadaan; Does the one whom Janaabah comes upon breaks his fasting, and what is obligatory upon him to do?

Answer: Your question manifests the affair of the one who had a (wet) dream- meaning: You slept and had a dream and Janaabah came upon you, and not by way of sexual intercourse; rather you had a dream. So, have you broken your fasting?  Your fasting is sound [i.e. valid and not nullified],  however what is incumbent upon you is to take a bath, but (wet) dream during sleep does not ruin the fast. Your fasting is correct and nothing is incumbent upon you Inshaa-Allaah; rather what is incumbent upon you is to perform the bath of Janaabah only.

This did not take place due to sexual intercourse and what is well known [to ruin the fast] is sexual intercourse whilst being awake. This is what is disallowed and forbidden, and there is expiation for it. The [scholarly] statement about the sleeping person is that if he has a (wet) dream whilst sleeping, then his fasting is correct and what is incumbent upon him is to take a bath.

[Al-Fataawaa Wad-Duroos Fil Masjidil Haraam of Shaikh Abdullaah Bin Muhammad Bin Humaid (rahimahullaah) Page: 507]