[Explanation]
The author—may Allah have mercy on him—relates from Abu Hurayrah (may Allah be pleased with him) that the Prophet (blessings and peace be upon him) said: “Allah has left no excuse for a person whose term of life He postpones until he reaches sixty years of age.”

The meaning is that when Allah allows someone to live to sixty, He has conclusively established the proof against him and removed any plea he might offer. Being kept alive for sixty years gives a person ample time to recognize Allah’s signs—especially if he was brought up in a Muslim country—so when he meets Allah he will have no defense. Had his life ended at fifteen or twenty, he might have argued that he had not had time to reflect upon the signs; but once Allah lets him reach sixty, that argument is invalid— the proof is complete.

In fact, the proof is binding from the moment a person attains puberty, for that is when legal responsibility begins and ignorance is no excuse. Each individual must therefore learn from the Sharia whatever he needs for his worship and daily dealings. If he wants to perform ablution, he must know how to do so properly; if he intends to pray, he must know how to pray. When he acquires wealth, he must learn the nisab, the amount of zakah due, and related rulings. If he plans to fast, he must know how to fast and what invalidates the fast. Should he wish to perform Hajj or ʿumrah, he must know the rites and the prohibitions of ihram. Likewise, a merchant who buys and sells gold, for example, must understand the rulings on usury, its various forms, and the conditions for selling gold for gold or gold for silver, and so forth.