Surah Maryam 19:21

قَالَ كَذَٰلِكِ قَالَ رَبُّكِ هُوَ عَلَىَّ هَيِّنٌ ۖ وَلِنَجْعَلَهُۥٓ ءَايَةً لِّلنَّاسِ وَرَحْمَةً مِّنَّا ۚ وَكَانَ أَمْرًا مَّقْضِيًّا

He said, "Thus [it will be]; your Lord says, 'It is easy for Me, and We will make him a sign to the people and a mercy from Us. And it is a matter [already] decreed.'"

Translation: Saheeh International

Tafsir

He said ‘It the matter in question of creating a boy from you without a father shall be so! Your Lord has said “It is easy for Me in other words by Gabriel’s breathing into you by My command so that you become pregnant with him — since what has been mentioned is meant as a reason the following statement is added as a …

Excerpt from Tafsir al-Jalalayn, commentary on 19:21, via Quran.com. The reader has the full commentary and 9 more tafsirs.