Here is the purpose of Adhyay 4 of Bhagavad Gita.
sannyasam karmanam krsna
punar yogam ca samsasi
yac chreya etayor ekam
tan me bruhi su-niscitam
And, in the Fourth Chapter, the Lord told Arjuna that all kinds of sacrificial work culminate in knowledge. However, at the end of the Fourth Chapter, the Lord advised Arjuna to wake up and fight, being situated in perfect knowledge. Therefore, by simultaneously stressing the importance of both work in devotion and inaction in knowledge, Krsna has perplexed Arjuna and confused his determination. Arjuna understands that renunciation in knowledge involves cessation of all kinds of work performed as sense activities.
But if one performs work in devotional service, then how is work stopped? In other words, he thinks that sannyasam, or renunciation in knowledge, should be altogether free from all kinds of activity because work and renunciation appear to him to be incompatible. He appears not to have understood that work in full knowledge is nonreactive and is, therefore, the same as inaction. He inquires, therefore, whether he should cease work altogether, or work with full knowledge.