What is the meaning of the Hadith: "There is no ghirar in prayer, nor taslim"?

The meanings of the Hadith (لا غرار في صلاة ولا تسليم - No ambiguity in prayer nor in greeting) can be summarized as follows:

1. No ambiguity in prayer: A worshiper should not exit their prayer in doubt, but rather certain of its completion. If they doubt its deficiency, they should base their action on the minimum (number of units) and complete their prayer, then perform the two prostrations of forgetfulness (sujud as-sahw). Ambiguity also includes deficiencies in bowing, prostrating, and tranquility, which must be perfected. 2. Nor in greeting: If "at-taslim" (التسليم) is recited with a kasra (genitive case): There should be no deficiency in returning a greeting. Rather, one should fulfill the right of the greeting by returning it in kind or better. If "at-taslim" (التسليم) is recited with a fatha (accusative case): It is not permissible to greet a worshiper, nor for the worshiper to greet anyone. If greeted, the worshiper should respond with a gesture.