In order to understand its significance, it should be kept in view that Allah has taken upon Himself to persuade human beings to adopt Islam of their free will, for He does not force His will on man in those spheres of his life in which He has granted him freedom of action but likes to convince him by reason and admonition.
As it is the work of Allah to bring the people to the right way by admonition and advice, He calls those people who exert their utmost to establish Islam "His helpers and companions". This is indeed the highest position that a servant of Allah can aspire to achieve.
For man's position is merely that of a servant when he is engaged in praying, fasting and other kinds of worship, but he is elevated to the high and unique position of God's companion and assistant when he is exerting for the establishment of the way of Allah. And this is indeed the loftiest position of spiritual attainment, to which a man can aspire in this world.
Comment: Let us be Allah's helpers. Why not?
Ref: Sayyid Abul Ala Maududi - Tafhim al-Qur'an - The Meaning of the Qur'an,Surah Al i Imran (The Family of Imran), verse 52-53. Footnote No 50. http://www.englishtafsir.com/Quran/3/index.html#sdfootnote50sym