Ruling on offering a sacrifice when building of the mosque is completed
Question

                When the building of a mosque is completed, some people say that it is not permissible to deliver a Jumu’ah khutbah or to offer any of the prescribed prayers in it until some cows or sheep have been bought, then people are invited and these animals are slaughtered and a feast prepared for the people. If this is not done, they claim that the imam of the mosque will die before his time if he prays in the mosque. Is this correct?.
Praise be to Allah.There is no basis for any of this; these 
    beliefs are all wrong. Those who believe that or do that should be denounced, because this is a bid’ah or innovation introduced into the religion, 
    and every bid’ah is a going astray, as the Prophet  (peace and blessings of Allaah be upon him) said in the saheeh hadeeth: “Whoever does an 
    action that is not part of this matter of ours (i.e., Islam), it is to be rejected.” 
 Narrated by Imam Muslim in his 
    Saheeh.