Is it allowed for the husband who is not fasting to have intercourse in the day in Ramadan?
Please answer giving surah explanation.
He could have intercourse, but this can only happen if his wife is also allowed to eat during the day in Ramadan!
Most scholars (Imam Malik, Imam Ash-Shafi'i and Imam Ahmad in one of his statements) say that any body who was allowed to eat at the beginnig of the day shouldn't fast according to a narration (not a hadith!) from ibn Masu'd (may Allah be pleased with him) saying " من أكل أول النهار فليأكل آخره who ate at the beginning of the day (this means after dawn) have to eat at the end of the day (this means sunset)" As an Answer for the Question saying: "A man who did suhur thinking it is night and found out that dawn has already past". By the way they also take the Verse 187 from Surat al Baqara (2) as a reference which states when one has the end and beginning times of fast!
As an example of practice a Tabi'i called abu Sha'ta' أبو الشعثاء came from a journey back home in Ramadan while his wife just made ghusl from menstruation and they had a physical relationship as narrated by Jabir ibn Yazyd جابر بن يزيد.
Here's a fatwa (in Arabic)