Canto 3 -
Araṇya-kāṇḍa
Chapter 56: Sītā is Taken to Aśoka-vana
Text 3.57.9

स ते जीवितशेषस्य राघवोऽन्तकरो बली।
पशोर्यूपगतस्येव जीवितं तव दुर्लभम्॥

sa te jīvita-śeṣasya rāghavo ’nta-karo balī
paśor yūpa-gatasyeva jīvitaṁ tava durlabham

saḥ = that; te = your; jīvita-śeṣasya = the remaining portion of life; rāghavaḥ = Rāghava; antakaraḥ = can annihilate; balī = mighty; paśoḥ = an animal; yūpa-gatasya = tied to a sacrificial pillar; iva = you are like; jīvitam = to live; tava = for you; durlabham = it is impossible.

That mighty Rāghava can annihilate the remaining portion of your life. You are like an animal tied to a sacrificial pillar. It is impossible for you to live.

[Rāvaṇa] is like an animal tied to a sacrificial pillar because he has offended Lord Rāma.