The word(s) "solemnly" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Pickthal translation.

(1) And whoso disputeth with thee concerning him, after the knowledge which hath come unto thee, say (unto him): Come! We will summon our sons and your sons, and our women and your women, and ourselves and yourselves, then we will pray humbly (to our Lord) and (solemnly) invoke the curse of Allah upon those who lie.

(2) They swear by Allah solemnly that, if thou order them, they will go forth. Say: Swear not; known obedience (is better). Lo! Allah is Informed of what ye do.