"Allah's Messenger (S) performed Salat until his feet were swollen, so it was said to him: 'You burden yourself like this, while your past and future sins have been forgiven?' He said: 'Shouldn't I be a grateful worshipper?'"
Jami` at-Tirmidhi Book 2, Hadith 265
← Previous Hadith They were with the Prophet (S) on a journey. They wound up in a narrow area when Salat became due. Then it began raining from the sky above them, and it was wet beneath them. So Allah's Messenger (S) called the Adhan while he was on his mount, and then the Iqamah, going forward on his mount. He let them in Salat by making gestures, making his prostrations lower than his bowing.

Jami` at-Tirmidhi Book 2, Hadith 264 Next Hadith → "I arrived in Al-Madinah and said: 'O Allah! Facilitate me to be in a righteous gathering.'" He said: "I sat with Abu Hurairah and said: 'Indeed I asked Allah to provide me with a righteous gathering. So narrate a hadith to me which you heard from Allah's Messenger (ﷺ) so that perhaps Allah would cause me to benefit from it.' He said: 'I heard Allah's Messenger (ﷺ) say: "Indeed the first deed by which a servant will be called to account on the Day of Resurrection is his Salat. If it is complete, he is successful and saved, but if it is defective, he has failed and lost. So if something is deficient in his obligatory (prayers) then the Lord, Mighty and Sublime says: 'Look! Are there any voluntary (prayers) for my worshipper?' So with them, what was deficient in his obligatory (prayers) will be completed. Then the rest of his deeds will be treated like that."

Jami` at-Tirmidhi Book 2, Hadith 266