Is it permissible for me to stop praying with an imam who is ignorant of some of the rulings of prayer and combines prayers during light rain, and pray in a mosque close to work?

First: The person who has memorized the Book of Allah and is knowledgeable of the rulings of prayer is to be put forward to lead the prayer. It is not prescribed to appoint an ignorant person as a regular imam.

Second: It is not prescribed to combine prayers due to light rain that does not cause harm. Whoever combines prayers because of it has erred. However, if people differ in their estimation of the rain, and the imam deems that it permits combining prayers, he is allowed to do so. The worshipper may combine with him to attain the virtue of congregational prayer. If he fears discord, he should pray with them intending it as a supererogatory prayer, and then pray 'Isha' at its prescribed time in another mosque.

Third: Renewing ablution is a Sunnah according to the majority of jurists.

Fourth: The prostration of forgetfulness consists of two prostrations, not one. If someone prostrates once due to ignorance, his prayer and the prayer of those behind him are valid. The worshippers should perform the second prostration.

Fifth: The general rule for obligatory prayers is that they should be performed in the houses of Allah. Praying in a workplace prayer area is not permissible except in case of necessity. It is preferable to pray in a nearby mosque, and this is further emphasized if the imam is not concerned with the rulings of prayer.