Aal-'Imran - 3:139

وَلاَ تَهِنُوا وَلاَ تَحْزَنُوا وَأَنتُمُ الأَعْلَوْنَ إِن كُنتُم مُّؤْمِنِينَ
[3:139]
And be not infirm, and be not grieving, and you shall have the upper hand if you are believers.
So lose not heart, nor fall into despair: For ye must gain mastery if ye are true in Faith.
Faint not nor grieve, for ye will overcome them if ye are (indeed) believers.