Jami` at-Tirmidhi 38
جامع الترمذي#38SahihAsim bin Laqit bin Sabirah narrated from his father that :the Prophet Muhammad said: "When performing Wudu go between the fingers
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih
In-book reference: 1:38