It is narrated from Hazrat Muhajir bin Qunfudh (may Allah be pleased with him) that once the Prophet (peace and blessings be upon him) was urinating or had just finished urinating. I greeted him with salam, but he did not reply until he had performed ablution, and then he replied to me.
Hadith Referenceمسند احمد / أول مسند البصريين / 20762
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد منقطع، الحسن لم يسمعه من حضين ماشرة