Sayyiduna Abdullah bin al-Sa'ib (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "The prayer of one who sits is half the prayer of one who stands."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains a narrator, Abd al-Karim bin Abi al-Mukhariq, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2904