Al-Ahnaf bin Qays relates: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said to me: "O Ahnaf! Whoever laughs a great deal, his awe is lessened; whoever jests is taken lightly; whoever speaks a great deal, his idle talk is also great; whoever's idle talk is great, his modesty is little; whoever's modesty is little, his piety is little; and whoever's piety is little, his heart dies."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains Duwayd bin Mujashi', whom I do not know, and the rest of its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الزهد / 18173