The most beloved deed to the Messenger of Allah ﷺ was the one performed consistently, even if it was small.
حدثنا وكيع حدثنا سفيان عن أبي إسحاق عن أبي سلمة بن عبد الرحمن
كان أحب العمل إلى رسول الله ﷺ ما دام عليه وإن قل
Its isnad is sahih. It was mentioned previously at 26588.