Canto 2 -
Ayodhyā-kāṇḍa
Chapter 22: Rāma Instructs Lakṣmaṇa
Text 2.22.21

कश्च दैवेन सौमित्रे योद्धुमुत्सहते पुमान्।
यस्य न ग्रहणं किञ्चित्कर्मणोऽन्यत्र दृश्यते॥

kaś ca daivena saumitre yoddhum utsahate pumān
yasya na grahaṇaṁ kiñcit karmaṇo ’nyatra dṛśyate

kaḥ ca = which; daivena = against providence; saumitre = O son of Sumitrā; yoddhum = to battle; utsahate = would be eager; pumān = man; yasya = it; na = cannot; grahaṇam kiñcit = [even] the means to recognize; karmaṇaḥ = through its effects; anyatra = except; dṛśyate = be perceived.

O son of Sumitrā, which man would be eager to battle against providence? [Even] the means to recognize it cannot be perceived except through its effects.

Under these circumstances, which man would be enthusiastic to fight against it? In other words, who is capable of restraining it?

What is the effect of providence that He is referring to here?  That is described in the next verse.