It was Prophet Isa (as). Injil is also known as the Bible.

Injil is Arabic word which is believed to be revealed Jesus but no any Christian knows that bible isn't written by Jesus or revealed by Jesus it was written by followers of Jesus and injil was completed revolved text from God which is not present in its original form

H. A. Oppusunggu has written:

'Melayankan Injil melalui media'

Muslims believe, as God said in Quran (Muslims Holy book), that the Bible (or Injil) is God revelation to Jesus. However, the current texts, with current languages, were written by the close companions to Jesus (peace be upon him) or to his followers.

For more information on who wrote the Old Testament and the New Testament, it could be referred to the related links below.

Yusuf A. Lubis has written:

'Penjelasan tentang Taurat dan Injil' -- subject(s): Islamic interpretations, Bible