All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad (saw) is His slave and Messenger.The dear questioner has made a vow to Allaah, the Exalted, that if He grants him success in building three floors, he will slaughter a calf and dedicate its reward to his dead parents. Slaughtering a sacrificial animal is an act of obedience to Allaah, the Exalted, as He says (what means): {So pray to your Lord and sacrifice [to Him alone].} [Quran 108:2] Offering charity on behalf of the deceased is an act of obedience to Allaah, the Exalted, as well. Abu Hurayrah reported the following: "A man came to the Prophet, sallallaahu 'alayhi wa sallam, and said, "My father died and left behind wealth without making a will regarding it. Will he be relieved of the burden of his sins if I give charity on his behalf?" The Prophet, sallallaahu 'alayhi wa sallam, said: "Yes."  [Ahmad and Muslim] According to most scholars, it is incumbent on the person to deliver on this kind of vow. 'Aishah narrated that the Prophet, sallallaahu 'alayhi wa sallam, said: "Whoever vowed to do an act of obedience to Allaah, the Exalted, must do it." [Al-Bukhari and Muslim]Allaah Knows best. (Source: islam_web) Classified in Etiquettes, Morals, Thikr and Du'aa' > Etiquette of Daily Practice