Ya ayyuha allatheena amanoo ittaqoo Allaha wabtaghoo ilayhi alwaseelata wajahidoo fee sabeelihi (surah Maidah: 35)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(5:35) Believers! Fear Allah and seek the means to come near to Him, *58 and strive hard in His way; *59 maybe you will attain true success.

yaaa aiyuhal lazeena aamanut taqul laaha wabtaghooo ilaihil waseelata wa jaahidoo fee sabeelihee la`allakum tuflihoon

*58). People are urged to solicit all means which might bring them close to God and enable them to please Him.
*59). The English imperative 'strive hard' does not do full justice to the actual word used in the Qur'an: jahidu. The verbal form mujahadah signifies and carries the nuance of doing something in defiance of, or in opposition to someone. The true sense of the Qur'anic injunction 'strive hard' in the way of Allah is that the Muslims ought to use all their strength and engage in vigorous struggle against those forces which either forcefully prevent them from living in obedience to God or force them to live in obedience to others than God. It is this struggle which is likely to lead man to his true success and bring him to a close relationship with God.
This verse directs the believer to engage in a ceaseless, multifrontal struggle. On one side is the accursed Satan with his horde. Then comes the animal spirit of man, with its defiant and refractory desires. Then there are many men who have turned away from God, but with whom one is linked by social, cultural and economic ties. Then there are false religious, cultural and social systems which rest on rebellion against God and which force man to worship falsehood rather than Truth. These rebellious forces use different means to achieve their end, but those ends are always the same - to make men serve them rather than God. But man's true progress and his attainment of close communion with God depends entirely on his total obedience to God, on his serving God unreservedly in the inner as well as in the external aspects of his life. He cannot achieve this objective without engaging in simultaneous combat with all the forces which are defiant and rebellious towards God, carrying on an unceasing struggle against them and trampling down all obstructions to his advancement along God's path.