Among the Jews it was usual to stand to pray (see Mt. 6:5 and Lk. 18:11, 13). Kneeling for prayer, though it has become a regular Christian attitude, was formerly an expression of deep emotion or earnestness, and on that basis we must understand Paul's words here. Solomon knelt at the dedication of the temple (1 Ki. 8:54); Stephen at the time of his martyrdom (Acts 7:60); Peter at the death-bed of Dorcas (Acts 9:40); Paul at the tiem of his farewells on his last journey to Jerusalem (Acts 20:36; 21:5); our Lord himself in his agony in Gethsemane (Lk. 22:41).
Discussion: If it was unusual for Jews to kneel in prayer, then how should we understand the importance of what Paul prayed for in Ephesians 3? What is the significance of his prayer request?
Source: Foulkes, Francis (1989). Tyndale New Testament Commentaries: Ephesians. Inter-Varsity Press: Leicester, England. pp. 108-109.