What remains permitted and what is forbidden during the holy month of Ramadan stands, as ordained:
”Permitted to you on the night of the fasts, is the approach to your wives. They are your garments and ye are their garments. Allah knoweth what ye used to do secretly among yourselves: but He turned to you and forgave you; so now associate with them, and seek what Allah had ordained for you, and eat and drink, until the white thread of dawn appears to you distinct from its black thread, then complete your fast till the night appears, but do not associate with your wives while ye are in retreat in the mosques. Those are the limits (set by) Allah: approach not night thereto. Thus doth Allah make clear His Signs to men: that they may learn self-restraint” (2:187)
We may take into account that fasting during Ramadan is only from dawn to dusk. During these hours, restraint is advised not only for eating and drinking but also from what are otherwise natural activities like approaching wives. However, as soon as the prescribed hours of fasting are over, approach to wives is permitted; provision is made for fulfilling biological needs. The relationship between spouses is an intimate one; they are garments to each other. Garments fit the body, they suit the persona, yet they hide what may not be seen. There cannot be a better analogy. Men and women complement each other. They fill each other’s biological needs. Sex within prescribed norms should neither be a taboo, nor unduly advertised. There is a restriction however for not associating with wives, during retreat in mosques. Retreat in the mosques refers to ‘I’tikaf’ which was the practice of Prophet (pbuh) during the last ten days of Ramadan; the practice is followed by ardent lovers of Prophet (SaW).
Until the white thread of dawn appears to you distinct from its black thread is taken to mean the appearance of firstly the white indefinable streak of light in the east; before the supervening of dark zone; which is ultimately followed by beautiful pinkish white zone clearly defined from the dark; after that the fast begins. And, what is permitted during the intervening night remains forbidden till sunset.