What does it mean that Hazrat Mirza Ghulam Ahmad (as), the Promised Messiah, in his prayer for those attending the Jalsa, calls God the one who takes his place in caring for them?
The Arabic word used there means, in general, someone who takes the place of another in his absence. So the meaning is this. When I am not with you, God will care for you in my place.
The Jalsa Salana is the annual gathering to which people travel from far and wide. For those attending it, Hazrat Mirza Ghulam Ahmad (as), the Promised Messiah, wrote a detailed prayer. At its end he refers to God with an Arabic word that many know only as a title. Its basic meaning, however, is much wider.
This word describes someone who takes the place of another in his absence. He steps in where the other is missing and looks after everything the other would have looked after. The first verse above shows this clearly. When Moses (as) went away for a time, he asked his brother Aaron (as) to act for him among the people during that time.
When God steps in where a person cannot be, and takes care of everything that person wished to take care of, then in this sense God takes his place. That is exactly what the sentence in the prayer means. I cannot always be with you, but God will be, and you are under His protection.
This is not a new thought. Before every journey the Holy Prophet Muhammad (saw) said a prayer in which he called on God as the companion on the way and the guardian of those who stay at home, as the hadith above reports. The Arabic there uses the same word.
This makes it clear why the Promised Messiah (as) entrusted the guests of the Jalsa to God with this word. He knew that God is the best Protector, as the second verse above says.