Translation:

189. They ask thee concerning the new moons. Say: they are but signs to mark fixed periods of time in (the affairs of) men and for pilgrimage. It is no virtue if ye enter your houses from the back; it is virtue if ye fear Allah. Enter houses through the proper doors and fear Allah that ye may prosper.

Notes (Tafseer)

202. There were many superstitions connected with the New Moon, as there are to the present day. We are told to disregard such superstitions. As a measure of time, where the lunar calendar is used, the New Moon is one great sign, for which people watch with eagerness. Muslim festivals, including the Pilgrimage, are fixed by the appearance of the New Moon. The Arabs, among other superstitions, had one which made them enter their houses by the back door during or after the Pilgrimage. This is disapproved, for there is no virtue in any such artificial restrictions. All virtue proceeds from the love and fear of God.

203. This is a Muslim proverb now, and much might be written about its manifold meanings. A few may be notes here. (1) If you enter a society, respect its manners and customs. (2) If you want to achieve an object honourably, go about it openly and not "by a backdoor". (3) Do not beat about the bush. (4) If you wish success in an undertaking, provide all the necessary instruments for it.