Sunan Ibn Majah 774
سنن ابن ماجه#774SahihIt was narrated that Abu Hurairah said:"The Messenger of Allah said: 'When one of you performs ablution and does it well, then he comes to the mosque with no other motive but prayer and not seeking anything other than the prayer, he does not take one step but Allah raises him in status one degree thereby, and takes away one of his sins, until he enters the mosque. When he enters the mosque he is in a state of prayer so long as he is waiting for the prayer
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Fouad Abd al-BaqiSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih
In-book reference: 4:40