Praise be to Allaah.
I know, may Allaah teach us and you, that this is one of the myths and innovations that have no basis on the Qur’aan or Sunnah. It is like the things said by the people who follow innovations and are misguided, so that they say that it is makrooh to get married when the moon is in Scorpio or when it is under the rays [???], or when it is waning or in any of its other stages.(See Mu’jam al-Bida’ by Raa’id Sabri, 656).
Allaah has permitted intercourse at all times and in all places, with the following exceptions:
During the day in Ramadaan. Allaah says (interpretation of the meaning): “It is made lawful for you to have sexual relations with your wives on the night of al-siyaam (the fasts). They are libaas (body cover, screen, etc.) for you and you are the same for them. Allaah knows that you used to deceive yourselves, so He turned to you (accepted your repentance) and forgave you. So now have sexual relations with them and seek that which Allaah has ordained for you (offspring)…” [al-Baqarah 2:187]
During the woman’s period [hayd] and when she is still bleeding after childbirth [nifaas]. Allaah says (interpretation of the meaning): “They ask you concerning menstruation. Say: that is an adha (a harmful thing for a husband to have a sexual intercourse with his wife while she is having her menses), therefore keep away from women during menses and go not unto them until they have purified (from menses and have taken a bath). And when they have purified themselves, then go in unto them as Allaah has ordained for you…” [al-Baqarah 2:222]
In the mosques. Allaah says (interpretation of the meaning): “… And do not have sexual relations with them (your wives) while you are in I’tikaaf (i.e., confining oneself in a mosque for prayers and invocations leaving the worldly activities) in the mosques. These are the limits (set) by Allaah, so approach them not…” [al-Baqarah 2:187]
And in other situations, such as when one is muhrim (in a state of ihraam for Hajj or ‘Umrah). You will not find anything in the Qur’aan or Sunnah to confirm this lie. It is a kind of evil falsehood that has cheated a lot of people, so that now they hold it as some kind of inflexible belief. Many people have had intercourse with their wives on a Tuesday and have conceived healthy children. No harm has befallen either them or their children because of that. May Allaah protect us and you from bid’ah and evil. And Allaah knows best.