4 Then, stretching yourself out on your left side, take the sin of the children of Israel on yourself: for as long as you are stretched out, so long will the sin of the children of Israel be on you. 5 For I have had the years of their sin measured for you by a number of days, even three hundred and ninety days: and you will take on yourself the sin of the children of Israel. 6 And when these days are ended, turning on your right side, you are to take on yourself the sin of the children of Judah: forty days, a day for a year, I have had it fixed for you.
Matthew Henry's Commentary on Ezekiel 4:4-6
Commentary on Ezekiel 4:1-8
(Read Ezekiel 4:1-8)
The prophet was to represent the siege of Jerusalem by signs. He was to lie on his left side for a number of days, supposed to be equal to the years from the establishment of idolatry. All that the prophet sets before the children of his people, about the destruction of Jerusalem, is to show that sin is the provoking cause of the ruin of that once flourishing city.