Rashi on Numbers
יאר ה' פניו אליך THE LORD MAKE HIS FACE SHINE UPON THEE — i.e. May He show thee a friendly (more lit., smiling) countenance — a beaming countenance.
Sforno on Numbers
יאר, may He grant light to your eyes to see and appreciate all the wonderful things G’d has done and keeps on doing. You should become aware that all that you achieve is due to His blessing.
Or HaChaim on Numbers
יאר ה׳ פניו, "May the Lord make His face shine upon you." This means that there should not be a "curtain" dividing between Israel and their Father in Heaven.