וּבְנֵיהֶ֞ם אֲשֶׁ֣ר לֹֽא־יָדְע֗וּ יִשְׁמְעוּ֙ וְלָ֣מְד֔וּ לְיִרְאָ֖ה אֶת־יְהוָ֣ה אֱלֹהֵיכֶ֑ם כָּל־הַיָּמִ֗ים אֲשֶׁ֨ר אַתֶּ֤ם חַיִּים֙ עַל־הָ֣אֲדָמָ֔ה אֲשֶׁ֨ר אַתֶּ֜ם עֹבְרִ֧ים אֶת־הַיַּרְדֵּ֛ן שָׁ֖מָּה לְרִשְׁתָּֽהּ׃ (פ)
E os filhos deles, que não sabem, ouvirão e aprenderão a temer ao Eterno vosso Elohim todos os dias que viverdes sobre a terra, à qual estais passando o Yarden para possuí-la. {פ}
Kli Yakar
And their children who did not know, etc. If this verse is speaking about young children who have reached the age of education, then it makes sense when it says “they will hear and learn to fear the Lord,” because they still do not know anything about the fear of the Lord. But regarding adults, it says “so that they may hear and so that they may learn and fear the Lord,” because they only need to hear and learn the commandments, but regarding fear, they will naturally fear the Lord on their own, as they are already accustomed to fearing the Lord all day long.
However, if this verse is speaking about future generations, it seems appropriate to interpret this in the way it is stated in Parashat Ekev And now, Israel, what does the Lord ask of you but to fear, etc. (Deuteronomy 10:12). Because it is written afterward, not with your children who did not know and who did not see the discipline of the Lord your God, etc. continuing until for your eyes have seen all the great work of the Lord. For he wanted to explain with this what was written above, And now, Israel, what does the Lord your God ask of you but to fear. Is fear such a small matter? To this he said: If I were speaking with your children who did not see the discipline of the Lord and were not rooted in the fear of the Lord, certainly I would be asking of them something very great. However, I am speaking with you, for your eyes have seen all the great work of the Lord which God performed so that people would fear Him, as it says so that His fear may be before you, etc. (Exodus 20:17). And for you, I am certainly asking for something small, because even though fear is something of great value, nevertheless for you it is easy to fulfill, because you are already rooted in fear. This is what is meant by And now, Israel. With the word now, he concluded all his words, saying that now, in this generation, it is a small matter, and what does the Lord ask of you now but to fear.
And this is what it says here about that generation: so that they may hear and so that they may learn and fear the Lord, because regarding fear, they do not need so much encouragement, and they will fear the Lord on their own. And their children who did not know is exactly similar to the statement not with your children who did not know, etc. And with this, he meant that your children who did not know the discipline of the Lord and did not see His greatness need encouragement and instruction about fear. And this is what it says: they will hear and learn to fear the Lord, because for them, fear is a very great matter.
However, if this verse is speaking about future generations, it seems appropriate to interpret this in the way it is stated in Parashat Ekev And now, Israel, what does the Lord ask of you but to fear, etc. (Deuteronomy 10:12). Because it is written afterward, not with your children who did not know and who did not see the discipline of the Lord your God, etc. continuing until for your eyes have seen all the great work of the Lord. For he wanted to explain with this what was written above, And now, Israel, what does the Lord your God ask of you but to fear. Is fear such a small matter? To this he said: If I were speaking with your children who did not see the discipline of the Lord and were not rooted in the fear of the Lord, certainly I would be asking of them something very great. However, I am speaking with you, for your eyes have seen all the great work of the Lord which God performed so that people would fear Him, as it says so that His fear may be before you, etc. (Exodus 20:17). And for you, I am certainly asking for something small, because even though fear is something of great value, nevertheless for you it is easy to fulfill, because you are already rooted in fear. This is what is meant by And now, Israel. With the word now, he concluded all his words, saying that now, in this generation, it is a small matter, and what does the Lord ask of you now but to fear.
And this is what it says here about that generation: so that they may hear and so that they may learn and fear the Lord, because regarding fear, they do not need so much encouragement, and they will fear the Lord on their own. And their children who did not know is exactly similar to the statement not with your children who did not know, etc. And with this, he meant that your children who did not know the discipline of the Lord and did not see His greatness need encouragement and instruction about fear. And this is what it says: they will hear and learn to fear the Lord, because for them, fear is a very great matter.
Sforno
ובניהם אשר לא ידעו, seeing that due to their tender age they are unable to formulate their questions if they have any.
Or HaChaim
ובניהם אשר לא ידעו, "and their children, who do not know, etc." This division is in line with mention of "and the children" in verse 12 as part of the מצוה of הקהל. Moses says that although he is aware that the children are too young to understand what they would hear at that assembly, they are not too young to learn to fear G'd, i.e. one must train them in יראת השם from an early age.