Marrying off a sister before her older sister

Q 1, 2: Here in Egypt we have special customs and traditions. Among these customs is the prohibition of marrying the younger daughter before the older one. Is there any evidence to the opposite? What is the ruling on putting such customs into practice? In which case should customs and traditions be given priority over Shari`ah (Islamic law)?Is the Hadith stating: You have better knowledge (of a technical skill) in the affairs of the world Sahih (authentic)? If yes, we hope that you, helped by Allah (Glorified and Exalted be He), explain the Hadith to us pointing out when it should be enforced, to what it is applicable, whether it is applicable to the issue at hand and whether applying the Hadith here inflicts injustice on the younger daughter and whether every issue has its own discretionary judgment.

(Part No. 18; Page No. 27) A: The basic principle is the general permissibility that daughters are given in marriage, whether they are young or old. Allah (Exalted be He) said: And marry those among you who are single (i.e. a man who has no wife and the woman who has no husband) and (also marry) Thus, if a woman is asked in marriage from her guardian when all the requirements are met and impediments do not exist, the guardian should give her in marriage. Actually, the custom of marrying the younger daughter before the older one does not go against Shari`ah. As for the Hadith that reads: You have better knowledge (of a technical skill) in the affairs of the world, it is Sahih as it is related by Muslim in his Sahih (authentic book of Sunnah). It means that people have better knowledge and more technical skill regarding worldly affairs such as farming, industries, weaving, trade and the like. However, the Shar`y (Islamic legal) ruling on all affairs has to be taken into consideration. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.