Dua for the Ruku (bowing in prayer)

  ''O Allah, to You I bow (in prayer) and in You I believe and to You I have submitted. Before You my hearing is humbled, as is my sight, my mind, my bones, my nerves and what my feet have mounted upon (for travel).''

Allaahumma laka raka'tu, wa bika 'aamantu, wa laka 'aslamtu khasha'a laka sam'ee, wa basaree, wa mukhkhee, wa 'adhmee, wa 'asabee, wa mastaqalla ...bihi qadamee.

اللَّهُمَّ لَكَ رَكَعْتُ، وَبِكَ آمَنْتُ، وَلَكَ أَسْلَمْتُ خَشَعَ لَكَ سَمْعِي، وَبَصَرِي وَمُخِّي، وَعَظْمِي، وَعَصَبِي، وَمَا اسْتَقَلَّ بِهِ قَدَمِي

Muslim 1/534, Abu Dawud, An-Nasa'i and At- Tirmidhi.