The wording used in this verse indicates an ongoing process of working by day and sleeping by night over a period of time. Jesus highlighted what happened during that time.
وَلكِنْ هَلْ يُعْقَلُ ٱلْقَوْلُ إِنَّ يَسُوعَ يَنَامُ وَلَا يَعْرِفُ كَيْفَ يَنْمُو ٱلْبِذَارُ ؟‏ !‏