The Ruling on Abandoning Voluntary Acts of Worship

Question : It is permissible by the Shari'ah to abandon a voluntary act of worship.

Answer : The answer is yes, it is permissible by the Shari'ah. The discussion concerns the Shari'ah, provided that it does not involve Hajj or 'Umrah, for abandoning those is prohibited. What is the evidence for the permissibility of abandoning a voluntary act of worship? The evidence is that the Messenger (peace and blessings be upon him) entered his home one day, and his family said to him, “A gift of hais has been given to us.” Hais is dates mixed with ghee and flour, or with ghee and dried milk. He said, “Show it to me, for I have fasted this morning.” So he ate from it. This was a voluntary fast. This indicates the permissibility of abandoning a voluntary act of worship. But...
The scholars said that it is disliked to abandon a voluntary act of worship except for a valid reason. This is because abandoning it without a valid reason involves a degree of turning away from the worship of Allah and obedience to Allah, because it is said, “Now you have started. You began the worship and entered into it. How do you turn away from Allah the Exalted and Majestic when you have just begun your worship of Him?”
Were it not for this hadith, we would have said that whoever begins a voluntary act of worship is obligated to complete it. This is because beginning an act of worship resembles a vow in some respects, as if he entered into it committed to performing it in full. But because of this hadith, the scholars said that it is permissible to abandon it, but it is disliked except for a valid reason. A man delayed in order to pray. In the middle of the prayer, he abandoned it. Is that permissible or not? It is permissible, but it is disliked except for a valid reason.