﴿ ٱلْحَقُّ مِن رَّبِّكَ ۖ فَلَا تَكُونَنَّ مِنَ ٱلْمُمْتَرِينَ ﴾

“the truth from thy Sustainer! Be not, then, among the doubters:”

The truth comes from your Lord; then be not among the doubters who doubt it that is to say ‘be not of such a disposition’ which is more eloquent than merely saying ‘do not waver’.