“Performing ablution thoroughly despite hardship.” (1) But we do not say to a person: if you are able to heat the water, it is better for you to use cold water and not heat it. We do not say this. So long as Allah has made things easy for you, make them easy for yourself.

His statement, “Nor is completion obligatory in a voluntary act,” means that completing a voluntary act of worship is not obligatory. The evidence for this is that the Prophet ﷺ once entered upon his family and said, “Do you have anything?” They replied, “Yes, we have hays.” He said, “Show it to me”—addressing Aishah—“for I began the day fasting.” She showed it to him, and he ate. (2) He also said, “The likeness of fasting—or he said, voluntary fasting—is like charity which a man gives from his wealth: if he wishes, he carries it through, and if he wishes, he withdraws it.” (3)

This fast was voluntary, and the Prophet ﷺ discontinued it and ate. This shows that voluntary worship is flexible: a person may discontinue it. However, the scholars say that he should not discontinue it except for a sound reason.

An example is when you are invited to a wedding feast while fasting: you supplicate for the hosts but do not eat. Yet if eating would gladden your host’s heart, then you should eat. This means that you have ended your fast, but in this case leaving the fast is for a sound reason: gladdening the heart of your Muslim brother.