Reference: Majmoo’ al-Fataawa wal-Maqaalaat al-Mutanawwi’ah – Volume 10, Page 99
Question: Is it a condition for the one who has a thick beard, that the water reaches the roots [when doing wudhoo]?
Response: It is sufficient for him that water passes over it, since there are authentic narrations which suggest that. And if he was to comb through it [with his wet fingers], then that is better – as the Prophet ﷺ did [both] this and that.