When does One get Awarded for Going to the Congregational Prayer?

His (ﷺ) saying, "Then he went out of his house to the Masjid, nothing made him go out of his house except the prayer." This indicates that [one must] have an intention in order to gain this great reward. However, if he left his house not intending the prayer, then the reward would not be written for him. For example, if he leaves his house to go to a shop and when the Adhan is called he goes to pray, he will not gain this reward. That's because the reward is only for the one who only leaves his house for the prayer. However, the reward might be written for him from when he left the shop until he reached the Masjid, as long as he left that place while he was in a state of purity (i.e. he was on Wudu’).