Sayyiduna al-Muttalib bin Abi Wada'ah (may Allah be pleased with him) says: The Prophet (peace and blessings be upon him) saw a man praying sitting, and he said: "The prayer of one who (prays) sitting is half the prayer of one who (prays) standing." So the people took pains to stand.
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Salih bin Abi al-Akhdar, whom the majority graded da'if (weak), while Ahmad said: His hadith is to be taken into consideration.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2905