It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that when any one of you performs ruku', he should spread his arms over his thighs and join his two palms together, as if I am still seeing the spread fingers of the Prophet (peace and blessings be upon him). Saying this, he demonstrated by joining his two palms together in the state of ruku'. (This ruling has been abrogated).