Ka'b bin Ujrah (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) said: "O Ka'b, when you perform ablution, perform it well, and when you go out to the mosque, do not interlace your fingers, for you are in prayer."
This chain is sahih (authentic) if this al-Hasan bin Ali al-Raqqi memorised it accurately; I have not yet found anyone corroborating him in what he narrated of this.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5885