Meditation

Because Hanumanji is portrayed on the banner of Arjuna, it is
understood that Arjuna meditated on him during the battle, even though
Lord Krishna Himself is his chariot driver and tactical advisor in the
battle of Kuruksetra. This underscores the importance of sadhu in the
three-way check and balances system known as 'guru, sastra and sadhu.
Lord Krishna in this case is the guru and
Hanuman or Vajrangaji represents the sadhus.
In
the introduction to the Srimad Bhagavatam, Srila Prabhupada writes in
the Introduction to the Srimad Bhagavatam: "Arjuna was also a Vaisnava
devotee of Lord Krsna, and he fought valiantly for the satisfaction of
the Lord. Similarly, Vajrangaji, or Hanuman, was also a devotee of Lord
Rama, and he gave lessons to the non-devotee party of Ravana."
In
London on 17 July 1973 he said this during a lecture on the
Bhagavad-gita 1.20, "Just like nowadays also, every nation has
different types of flags, so Arjuna also had his flag,.Dhvajah means
the flag. The flag was on the top of his chariot. And it was marked
with Hanuman, Vajrangaji,.Hanuman, who fought for Lord Ramacandra,. He
is fighting for Krsna. So he is also following the footsteps of
Vajrangaji."