(3:139) So do not weaken and do not grieve, and you will be superior if you are [true] believers.
Muhammad Taqi-ud-Din al-Hilali and Muhammad Muhsin Khan,
(3:139) So do not become weak (against your enemy), nor be sad, and you will be superior (in victory) if you are indeed (true) believers.
Mohammed Marmaduke William Pickthall
(3:139) Faint not nor grieve, for ye will overcome them if ye are (indeed) believers.
Abdullah Yusuf Ali
(3:139) So lose not heart, nor fall into despair: For ye must gain mastery if ye are true in Faith.
Mohammad Habib Shakir
(3:139) And be not infirm, and be not grieving, and you shall have the upper hand if you are believers.
(3:139) And do not feel feeble nor grieve; and you are the most exalted in case you are believers.
(3:139) Do not, then, be faint of heart, nor grieve, for you are always the superior side if you are (true) believers.
Amatul Rahman Omar
(3:139) Therefore slacken not, nor grieve, and when you are true believers you shall certainly be the triumphant.
(3:139) And do not weaken/enfeeble , and do not be saddened/grieved, and you are the overcoming and becoming dignified/defeating, if you were believing.42
(3:139) So do not lose heart or be grieved, for you will surely prevail if you are believers.
A. J. Arberry
(3:139) Faint not, neither sorrow; you shall be the upper ones if you are believers.
Abdul Majid Daryabadi
(3:139) And faint not, nor grieve; ye shall overcome, if ye are believers.
Maulana Mohammad Ali
(3:139) Do not be discouraged or grieved. You alone will have true dignity if you only are true believers.
Hamid Abdul Aziz
(3:139) If a wound touches you, a similar wound has touched the others: these are only the vicissitudes of varying fortune which we bring in turn to mankind that Allah may know those who it is that believe, and may choose from you witnesses, for Allah loves not the unjust.
(3:139) And do not be negligent nor grieve – it is you who will be victorious if you are believers.
(3:139) And do not waver, nor feel remorse. You are the superior ones, if you are believers.
Ahmed Raza Khan
(3:139) And do not be negligent nor grieve it is you who will be victorious if you are believers.
(3:139) And do not become faint of heart, nor grieve, you will have the upper hand, if you are believers,
(3:139) So do not become weak, nor be sad, and you will be triumphant if you are indeed believers.
Ali Quli Qarai
(3:139) Do not weaken or grieve: you shall have the upper hand, should you be faithful.
Hasan al-Fatih Qaribullah and Ahmad Darwish
(3:139) Do not be weak, neither sorrow while you are the upper ones, if you are believers.
That is translated surah Ali ‘Imran ayat 139 (QS 3: 139) in arabic and english text, may be useful.