(7:21) And he swore [by Allah] to them, “Indeed, I am to you from among the sincere advisors.”
Muhammad Taqi-ud-Din al-Hilali and Muhammad Muhsin Khan,
(7:21) And he [Shaitan (Satan)] swore by Allah to them both (saying): “Verily, I am one of the sincere well-wishers for you both.”
Mohammed Marmaduke William Pickthall
(7:21) And he swore unto them (saying): Lo! I am a sincere adviser unto you.
Abdullah Yusuf Ali
(7:21) And he swore to them both, that he was their sincere adviser.
Mohammad Habib Shakir
(7:21) And he swore to them both: Most surely I am a sincere adviser to you.
Dr. Ghali
(7:21) And he swore to both of them, “Surely I am indeed for you both one of your honest (Literally: one of the honest advisers) advisers.”
Ali Unal
(7:21) And he swore to them: “Truly, I am for you a sincere adviser.”
Amatul Rahman Omar
(7:21) And he ardently swore to them both (saying), `Most certainly, I am one of your sincere advisers.´
Literal
(7:21) And he swore/made oath to them (B): “I am to you (B) from (E) the advisors/counselors.”
Ahmed Ali
(7:21) Then he said to them on oath: “I am your sincere friend;”
A. J. Arberry
(7:21) And he swore to them, ‘Truly, I am for you a sincere adviser.’
Abdul Majid Daryabadi
(7:21) And he sware unto them both: verily I am unto you of your good counsellors.
Maulana Mohammad Ali
(7:21)-
Muhammad Sarwar
(7:21) Satan swore before them that he was giving them good advice.
Hamid Abdul Aziz
(7:21) And he swore to them both, “Verily, I am unto you a sincere adviser;”
Faridul Haque
(7:21) And he swore to them, “Indeed I am a well-wisher for both of you.”
Talal Itani
(7:21) And he swore to them, I am a sincere advisor to you.
Ahmed Raza Khan
(7:21) And he swore to them, Indeed I am a well-wisher for both of you.
Wahiduddin Khan
(7:21) and he swore to them, “Surely, I am your well-wisher.”
Safi-ur-Rahman al-Mubarakpuri
(7:21) And he Qasamahuma: “Verily, I am one of the sincere well-wishers for you both.”
Ali Quli Qarai
(7:21) And he swore to them, I am indeed your well-wisher.
Hasan al-Fatih Qaribullah and Ahmad Darwish
(7:21) he swore to both: ‘Indeed, I am to you among the advisers’
That is translated surah Al A’raf ayat 21 (QS 7: 21) in arabic and english text, may be useful.