His statement, “and to praise Allah when he has finished,” means that it is recommended to praise Allah when one has finished. He should say, “Praise be to Allah,” for the Prophet ﷺ said: “Indeed, Allah is pleased with the servant who eats a meal and praises Him for it, or drinks a drink and praises Him for it.” (1) Undoubtedly, this is a form of gratitude to Allah, the Exalted, for His blessings: that He has made this food readily available to you. So praise Allah for that.
But should we say that this is done after one has finished eating altogether, or after every morsel and every drink?
What appears correct is the former, because even if the morsels are successive, they constitute a single meal. Thus, when he has finished his food, let him praise Allah.
For example, a man has rice before him and is eating it. Should we say: Every time you eat a mouthful, say, “Praise be to Allah”? Or is the sunnah that you praise Allah only when you have finished completely?
The answer is the latter.
Likewise, if a man is eating dates, do not tell him: Praise Allah every time you eat a date. So long as it is one meal, mention Allah’s name at its beginning and praise Him at its end.
His statement, “and to eat from what is nearest to him”: this applies when someone else is eating with him. It is part of good manners to eat from what is nearest to one, because the Prophet ﷺ said to Umar ibn Abi Salamah, his stepson: “Eat from what is nearest to you.” (2) This is also part of dignity and good etiquette. But if he is alone, he may eat from any side,