Musa عليه السلام took a companion with him, Yusha bin Nun عليه السلام, whom later became a Prophet of Allah himself – from this we learn the benefit of having a companion with you when seeking knowledge.

Good companions encourage you to do good deeds. The Prophet ﷺ said:
قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ “‏ مَثَلُ الْجَلِيسِ الصَّالِحِ وَالْجَلِيسِ السَّوْءِ كَمَثَلِ صَاحِبِ الْمِسْكِ، وَكِيرِ الْحَدَّادِ، لاَ يَعْدَمُكَ مِنْ صَاحِبِ الْمِسْكِ إِمَّا تَشْتَرِيهِ، أَوْ تَجِدُ رِيحَهُ، وَكِيرُ الْحَدَّادِ يُحْرِقُ بَدَنَكَ أَوْ ثَوْبَكَ أَوْ تَجِدُ مِنْهُ رِيحًا خَبِيثَةً ‏”
“A good friend and a bad friend are like a perfume-seller and a blacksmith: The perfume-seller might give you some perfume as a gift, or you might buy some from him, or at least you might smell its fragrance. As for the blacksmith, he might singe your clothes, and at the very least you will breathe in the fumes of the furnace.” [Bukhari]

This is a reminder that seeking knowledge is not an easy task, and it’s a given that you’ll face difficulties. Having a good companion will really benefit you during those difficult moments. While the emphasis is on having a friend or companion to be with you and who can help you and guide you, it is just as important to emphasise that the companion must be someone of sound judgement and must be sincere in his intentions and noble in his actions and deeds. If your “companion” is not on the right track, than it is very possible that he may be a bad influence on you and lead you away from your objective and be a big deterrent in you achieving your goals.

Another important point to keep in mind is that when you are seeking the knowledge of Deen, you will become the biggest enemy of Shaytaan. This is because a knowledgeable person is able to realise the tricks of Shaytaan and he will not allow himself to fall into those traps and he will guide others as well so as to prevent them from falling prey to the evils of Shaytaan. Therefore Shaytaan despises the seeker of Knowledge because he has the potential to ruin Shaytaan and his evil plots.
In this very story, both Musa and Yusha عليه السلام forgot about the fish – and as Allah mentioned that it was Shaytaan who made them forget.
وَمَآ أَنسَىٰنِيهُ إِلَّا ٱلشَّيْطَـٰنُ أَنْ أَذْكُرَهُ
“none but Shaytaan made me forget to tell (you) about it” [Al Kahf: 63]

Shaytaan causes the children of Adam to forget knowledge and forget to act upon it. To avoid this, we should always seek refuge in Allah and remember our adhkar when seeking knowledge or otherwise. Allah says:
إِنَّ ٱلَّذِينَ ٱتَّقَوْا۟ إِذَا مَسَّهُمْ طَـٰٓئِفٌ مِّنَ ٱلشَّيْطَـٰنِ تَذَكَّرُوا۟ فَإِذَا هُم مُّبْصِرُونَ
“Verily, those who fear Allah, when an evil thought comes to them from Satan, they remember (Allah).”

As the person seeking knowledge becomes the primary target of Shaytaan, it is very important for him to have a good companion who can help and guide him through the plotting of Shaytaan.