Say (O Muhammad SAW): "If the Most Beneficent (Allah) had a son

﴿قُلۡ إِن كَانَ لِلرَّحۡمَٰنِ وَلَدٞ فَأَنَا۠ أَوَّلُ ٱلۡعَٰبِدِينَ ﴾
[الزُّخرُف: 81]

Say (O Muhammad SAW): "If the Most Beneficent (Allah) had a son (or children as you pretend), then I am the first of Allah's worshippers [who deny and refute this claim of yours (and the first to believe in Allah Alone and testify that He has no children)]." [Tafsir At-Tabari]

﴿قل إن كان للرحمن ولد فأنا أول العابدين﴾ [الزُّخرُف: 81]

Al Bilal Muhammad Et Al
Say, “If God, the Merciful Benefactor had a son, I would be the first to worship him.”

Ali Bakhtiari Nejad
Say: if there was a child for the beneficent, then I would be the first of the servants

Ali Quli Qarai
Say, ‘If the All-beneficent had offspring, I would have been the first to worship [him].’

Ali Unal
Say: "If the All-Merciful had a child, I would be the first to worship

Hamid S Aziz
Say, "If the Beneficent has a son, I am the foremost of those who serve him

John Medows Rodwell
SAY: If the God of Mercy had a son, the first would I be to worship him

Literal
Say: "If (there) was to the merciful a child (son), so I am the worshippers` first/beginner

Mir Anees Original
Say, “If the Beneficent (Allah) had a son, then I would have been the first of the servants.”

Mir Aneesuddin
Say, “If the Beneficent (God) had a son, then I would have been the first of the servants.”