Rashi on Deuteronomy 33:6/רש"י על דברים ל״ג:ו׳

1יחי ראובן LET REUBEN LIVE, in this world,

2ואל ימת AND LET HIM NOT DIE, in the world to come (Sifrei Devarim 347:1) : that the incident of Bilhah be not remembered unto him (Sifrei Devarim 347:3).

3ויהי מתיו מספר lit., AND LET HIS MEN BE A NUMBER — let him be counted amongst the number of his other brothers. This is exactly similar to the idea that is expressed in the text, (Genesis 35:22) “[And Reuben went] and lay with Bilhah [his father’s wife]” … “And the sons of Jacob were twelve”, which suggests that he was not excluded from the number of Jacob’s sons.