9:122 wa maa kaanal mu'minuuna li yanfiruu kaaf-fah* falawlaa nafara min kul-li firqatim minhum Taaifatul li yatafaq-qahuu fid diyni wa li yundhiruu qawmahum idhaa raja'UU ilayhim la'Al-lahum yaHdharuun

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Ahmed Raza Khan: Mohammed Aqib Qadri:
And it is not possible for the Muslims that all of them go out; so it should be that a party from each group go forth in order to gain knowledge in religion, and upon returning warn their people in the hope that they may avoid.

Yusuf Ali:
Nor should the Believers all go forth together: if a contingent from every expedition remained behind, they could devote themselves to studies in religion, and admonish the people when they return to them,- that thus they (may learn) to guard themselves (against evil).

Pickthal:
And the believers should not all go out to fight. Of every troop of them, a party only should go forth, that they (who are left behind) may gain sound knowledge in religion, and that they may warn their folk when they return to them, so that they may beware.