Imam Hussain said: “Know that the evil of war is swift, and its taste is bitter. Therefore, he who prepares for it [war] sees to its requirements and does not suffer its wounds before its onset; he is its master. But he who plunges into it before its proper time and before gaining insight into his own effort therein, he is not fit to benefit his people, and [he] ruins himself [lit. his soul].”

الإمامُ الحسينُ (عَلَيهِ الّسَلامُ) : ألا إنَّ الحَربَ شَرُّها ذَريعٌ ، وطَعْمُها فَظيعٌ ، فمَن أخَذَ لَها اُهْبَتَها ، واسْتَعدَّ لَها عُدَّتَها ، ولَم يألَمْ كُلومَها قَبلَ حُلولِها ، فذاكَ صاحِبُها ، ومَن عاجَلَها قَبلَ أوانِ فُرْصَتِها ، واسْتِبْصارِ سَعيهِ فيها ، فذاكَ قَمِنٌ ألاّ يَنْفَعَ قَومَهُ ، وأنْ يُهْلِكَ نَفْسَهُ .

Sources

Mizan al-Hikma, hadith 4416; Sharh Nahj al-Balagha, Ibn Abi al-Hadid, vol. 3, pg. 186.