Bg 11.49

ma te vyatha ma ca vimudha-bhavo
drstva rupam ghoram idrn mamedam
vyapeta-bhih prita-manah punas tvam
tad eva me rupam idam prapasya

Word for word: 
ma — let it not be; te — unto you; vyatha — trouble; ma — let it not be; ca — also; vimudha-bhavah — bewilderment; drstva — by seeing; rupam — form; ghoram — horrible; idrk — as it is; mama — My; idam — this; vyapeta-bhih — free from all fear; prita-manah — pleased in mind; punah — again; tvam — you; tat — that; eva — thus; me — My; rupam — form; idam — this; prapasya — just see.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
You have been perturbed and bewildered by seeing this horrible feature of Mine. Now let it be finished. My devotee, be free again from all disturbances. With a peaceful mind you can now see the form you desire.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In the beginning of Bhagavad-gita Arjuna was worried about killing Bhisma and Drona, his worshipful grandfather and master. But Krishna said that he need not be afraid of killing his grandfather. When the sons of Dhrtarastra tried to disrobe Draupadi in the assembly of the Kurus, Bhisma and Drona were silent, and for such negligence of duty they should be killed. Krishna showed His universal form to Arjuna just to show him that these people were already killed for their unlawful action. That scene was shown to Arjuna because devotees are always peaceful and they cannot perform such horrible actions. The purpose of the revelation of the universal form was shown; now Arjuna wanted to see the four-armed form, and Krishna showed him. A devotee is not much interested in the universal form, for it does not enable one to reciprocate loving feelings. Either a devotee wants to offer his respectful worshipful feelings, or he wants to see the two-handed Krishna form so that he can reciprocate in loving service with the Supreme Personality of Godhead.